Thursday, 3 May 2012

The ultimate guide to renewable energy for your home


Energy is essential to the comfort of our homes, providing space and water heating and electricity. However, there are many ways in the design, construction and operation of our homes of reducing energy needs and meeting those needs with renewable sources, without compromising warmth and comfort.
     Currently, we rely heavily on fossil fuels such as coal, oil, and gas to provide our energy needs. Fossil fuels are non-renewable, that is, they draw on finite resources that will eventually run out. In contrast, renewable energy resources, provided from the sun, wind and water are constantly replenished and will never run out.
     Fossil fuels are also damaging to the environment. They contribute significantly to many of the environmental problems we face today such as greenhouse gases, air pollution, and water and soil contamination - while renewable energy technologies enjoy lower running costs and are clean sources of energy that have a much lower environmental impact.
     Energy is available from a variety of renewable sources appropriate to our homes, including solar, geothermal, biomass, hydro and wind.

Solar Energy

A horizontal surface of 1m2 receives an average of between 1,000 and 1,100 kWh of solar energy per year. This energy is provided by both direct sunlight (40%) and indirect sunlight (60%) and can be harnessed in many ways to heat your home, provide hot water and generate electricity.

Passive Solar Design

Passive solar design is a design approach that maximises the collection of solar heat, minimises heat loss from the building and provides natural ventilation and daylight.
     Unlike active solar heating systems,it doesn't involve the use of mechanical and electrical devices,such as pumps,fans or electrical controls to collect or store the solar heat.Instead energy costs are reduced and the comfort of your house increased by:
• selecting a sheltered location to build on
• constructing a compact building form with high levels of insulation
• positioning the house at an orientation that maximises passive solar heating and
daylight

Direct gain is the simplest passive solar design technique. It necessitates glazing to be concentrated to the south façade and minimised to the north façade.Sunlight enters the house through south-facing windows and is absorbed and stored in the masonry walls and floors.At night, as the room cools, the heat stored in the thermal mass convects and radiates into the room.This maintains a comfortable,even temperature in the home.

A well designed sunspace or conservatory on the south façade can also reduce the heating needs of a house by acting as a solar collector in late spring, summer and early autumn, and by acting as a buffer against heat loss at other times. It is important to choose a high performance glazing, at least double-glazing with a low emmisivity coating, to limit heat loss through glazed areas.However, there are many examples of sunspaces which are poorly designed from an energy point of view and increase heating requirements. Fully glazed conservatories should not be heated and should be separated from the heated space by closeable doors.They should not be regarded as being habitable all year round, as the energy losses from heated
conservatories can negate the energy saved by passive solar collection.
     Passive solar homes can look like any other home, and need not cost any more to build, but they are more comfortable to live in and cost less to run.

Active Solar for Space and Water Heating


Active solar energy systems generally incorporate a roof mounted solar collector,which receives direct and indirect sunlight and changes it into heat. This heat may be used to provide for hot water, or in a combined system, for space and hot water needs. At the end of 2003, approx. 12million m2 of solar thermal collectors were installed in the EU. There is great potential to increase this further.

How it works

Solar collectors can provide 60% of the annual hot water demand of a typical home, depending on the orientation, size, mounted angle and efficiency of the collector. The most common application is for water heating, and 4m2 of solar collector can provide about 80% of hot water needs in summer and 20% in winter (when there is less solar heat available) for a typical family. The solar water system needs to be backed up with a conventional heat source to provide the remainder of the hot water needs such as an electric immersion in the storage cylinder.

For more detail on how solar heats your water click here

For a great guide on how to create a DIY solar panel cheaply (that works) click here

Installation in the Home

Solar water heating systems for homes have two main parts: a solar collector and a hot water storage cylinder.
     Typically, a flat-plate collector (a thin, flat, rectangular box with a transparent cover) is mounted on the roof, facing the sun. The sun heats an absorber plate (usually a black metal plate) in the collector,which, in turn, heats the fluid running through pipes within the collector.To move the heated fluid between the collector and the storage cylinder, a system either uses a pump or gravity, as water has a tendency to naturally circulate as it is heated. Systems that use fluids other than water in the collector's pipes usually heat the water by passing it through a coil of tubing in the storage cylinder.
     Evacuated tube collectors can also be used instead of the flat plate. These consist of an array of evacuated glass tubes each containing an absorber tube, which collects solar energy and transfers it to a heat transfer fluid. During the manufacturing process, air is evacuated from the space between the two tubes, forming a vacuum. This vacuum greatly reduces heat loss from the system because there is no air to conduct the heat away. The heat absorbed by the collectors is then transferred to the hot water storage cylinder through a number of heat exchangers. Evacuated tube systems tend to be more efficient than flat plate systems. However, a similar output could be achieved with a flat plate system simply by increasing the area of the collector.
     Ideally, panels need to face directly south. However, a good output can still be achieved between south east and south west.A typical installation will take 2-3 days.
     Today, solar thermal systems are readily available, easy to install and are reliable in operation. Generally systems come with a 5-10 year warranty. A professional installer will advise on an optimised solution for
your specific needs.

Payback and Maintenance

The payback period of a solar water heating system will vary depending on the cost of the fuel you are replacing and the amount of hot water you consume. A typical correctly installed system has a payback period of between 7 and 15 years and little maintenance is necessary.Most systems are run by an electricity-powered pump,which will cost a small amount to run per year.Generally systems come with a 5-10 year warranty and their lifetime is about 25 years.

For a bit more detail on how solar energy can heat your water click here

Active Solar for Electricity


Photovoltaics (PV), which also collect sunlight, are a very different technology to solar water heating,as they use the light to generate electricity.Today,the industry’s production of photovoltaic (PV) modules is growing at approximately 25% annually, and major programs in the U.S.A., Japan and Europe are rapidly accelerating the implementation of PV systems on buildings and connection to electricity grid networks.

How it works

Photovoltaic solar cells, which directly convert sunlight into electricity, are made of semi-conducting materials, such as crystalline silicon.The power output of a PV cell depends on its efficiency and surface area, and is proportional to the intensity of sunlight striking the surface of the cell.
     Groups of PV cells are electrically configured into modules and arrays,which can be used to charge
batteries, operate motors, and to power electrical loads. With the appropriate power conversion equipment, PV systems can produce alternating current (AC) compatible with any conventional appliances, and operate in parallel with and interconnected to the electricity grid network. PV has the great advantages of being silent in operation with a low visual impact making them particularly suitable for urban areas.

There are two general types of PV systems, stand-alone and grid-connected systems:

Stand-Alone Systems

Stand-alone systems produce power independently of the electricity grid network. In some off-the-grid locations, stand-alone photovoltaic systems can be more cost-effective than extending existing power lines.      Direct-coupled systems need no electrical storage because they operate only during daylight hours, but most
systems rely on battery storage so that energy produced during the day can be used at night. Some systems, called hybrid systems, combine solar power with additional power sources such as wind or diesel generators. As well as domestic applications, stand-alone systems can be used to power traffic warnings, parking meters, emergency telephones and buildings in remote locations.

Grid-Connected Systems

Grid-connected photovoltaic systems, supply surplus power back onto the grid and electricity is drawn from the grid at periods when demand in the home exceeds the PV output. Grid-connected systems are generally integrated into the structure of buildings, but can also be ground mounted. These systems remove the need for battery storage. In some cases, utility companies allow additional metering, which allows the owner to sell excess power back to the utility company.

Installation in the Home

A PV array produces power when exposed to sunlight. They can be installed on an existing roof, be an integral part of the roof covering as panels or tiles installed within roof glazing systems or installed on a nearby structure. It is important that nothing casts a shadow over the area where the PV panels will be mounted. PV panels generate more electricity on bright days but do not require direct sunlight, so normal
daylight is sufficient to produce electricity.The ideal orientation for PV panels is south facing, although they still produce around 80% of the optimum output when facing east or west.
     A number of other components are required to properly conduct, control, convert, distribute, and store the energy produced by the array. Depending on the functional and operational requirements of the system, the specific components required, may include major components such as a DC-AC power inverter, battery
bank, system and battery controller, auxiliary energy sources and sometimes the specified electrical load.

Payback and Maintenance

PV is expensive, but with new materials and ongoing product development, it is expected that the price of PV cells will become more competitive in the future. In fact, the price has reduced by one third in the last ten years. Stand-alone systems often provide the most effective solution when grid electricity is not available.      For installations in larger buildings, cost savings are possible when PV panels are integrated in the building design,where they can substitute for other construction materials providing the external skin of a building. Today’s photovoltaic modules are extremely safe and reliable products, with minimal failure rates. Most major manufacturers guarantee the high efficiency operation of their PV modules for 20 or more years, with projected service lifetimes in excess of this. PV panels have no moving parts and require minimum maintenance.

Ground Source Heat Pumps


Ground source heat pumps, also known as geothermal heat pumps, are used for space heating and cooling, as well as water heating. They operate on the fact that the earth beneath the surface remains at a constant temperature throughout the year, and that the ground acts as a heat source in winter and a heat sink in summer. They can be used in both residential and commercial or institutional buildings.

How it works

The earth’s surface acts as a huge solar collector, absorbing radiation from the sun. In most countries the ground maintains a constant temperature between 11°C and 13°C, several metres below the surface. Ground source heat pumps take advantage of this by transferring the heat stored in the earth or in ground water to buildings in winter and the opposite in summer for cooling. Through compression, heat pumps can ‘pump up’heat at low temperature and release it at a higher temperature so that it may be used again. A heat pump looks similar and can perform the same functions as a conventional gas or oil boiler, i.e. space heating and sanitary hot water production. For every unit of electricity used to operate the heat pump, up to four units of heat are generated.Therefore for every unit of electricity used to pump the heat, 3-4 units of heat are produced.

Installation in the Home

The system has three main components:a series of pipes in the ground,a heat pump and a heat distribution system. Lengths of plastic pipes are buried in the ground, either in a borehole or a horizontal trench near the building to be heated or cooled. Fluid, normally water with anti-freeze, absorbs or emits heat to the soil, depending on whether the ambient air is colder or warmer than the soil. In winter, the heat pump removes the heat from the fluid, upgrades it to a higher temperature for use in the building, typically in under-floor heating.
     A distribution system is needed to transfer the heat extracted from the ground by the heat pump.The heat is often in the form of hot water and is distributed around the dwelling by radiators or a low temperature underfloor heating system.

Payback and Maintenance

The initial capital costs of installing a ground source heat pump system is usually higher than other conventional central heating systems. A large proportion of the outlay will be for the purchase and installation of the ground collector.However, the system is among the most energy efficient and cost effective heating and cooling systems available. Typically, four units of heat are generated for every unit of electricity used by the heat pump to deliver it, and the payback is typically about 8- 10 years.The life expectancy of the system is around 20 years. Once installed a heat pump requires very little maintenance and anyone installing a heat pump should speak with their installer regarding a maintenance agreement.

Biomass / Wood


The words biomass or bioenergy are used to describe energy resources derived from organic matter, such as residues from forestry, agriculture and industry, or from purpose grown crops. These resources can be used to provide heat, electricity and transport fuels. It provides about 1% of Ireland’s energy needs in the form of domestic and industrial wood heating. Using wood fuel instead of fossil fuels (oil, coal, gas or peat) makes a positive contribution to the environment. Wood, is a ‘carbon neutral’ fuel. It absorbs as much CO2 when it grows as is released when it burns – a natural cycle.Wood fuel takes just 5-20 years to grow,whereas fossil fuels such as peat and coal were formed over hundreds of thousands of years.
     The main types of wood fuel are chips and pellets.Wood chips are a bulk fuel and, as such, are generally unsuitable for domestic properties. However, they are usually a cheaper fuel than pellets and are appropriate for larger buildings such as offices, public buildings or to heat clusters of domestic properties through a district heating system.Wood pellets are compressed wood,usually sawdust or wood shavings.They are typically 6-12 mm in diameter and 6-20 mm in length. Pellets have the advantage of uniformity in shape and composition, are easy to ignite, are dry, create little ash and will flow freely through feeding mechanisms such as hoppers and augers.These properties make pellets ideal for automatic appliances.
     Wood fuel can be used to create both electricity and heat and is a well established renewable energy source in many countries, including the USA, Sweden,Austria and Denmark.

How it works

Pellets are highly suitable for houses and can be burned in either a boiler or a stove. Pellet boilers provide full central heating and hot water, with a convenience normally associated with oil or gas.
     Stoves provide heating for a single room. Stoves are available in a range of styles, from traditional-looking wood-burning stoves to modern, minimalist designs. Good quality appliances use modern controls to ensure an efficient, clean burning fire. Because they use thermostatic controls and fans to distribute warm air around the room they are safer than traditional stoves,which rely on radiated heat to warm the room, making the room's temperature uneven and the body of the stove dangerously hot.

Installation in the Home

The installation is similar to that of any central heating boiler or stove, and requires a flue and a fresh air supply to be installed for safe and efficient combustion.Many products are programmable to allow you to set the temperature that you require and some can even be controlled by mobile phone remote control.
     Stoves contain an integrated fuel hopper that must be filled manually.Once full, the hopper automatically supplies fuel to the stove, allowing it to operate independently for around 20-40 hours. For boilers or larger systems which require a greater fuel input, you may decide to site your storage facility adjacent to the boiler, and install a completely automatic fuel feed system, such as an auger, so that you do not have to re-fill the hopper manually. Fuel storage is an important consideration as pellets are a bulky fuel, requiring about three times the storage space of oil. However this requirement could be met with more frequent deliveries. The store must also be kept completely dry as pellets disintegrate on contact with water.

Payback and Maintenance

Maintenance is similar to that of conventional stoves and boilers. The ash pans of both stoves and boilers will require emptying, typically once per month for stoves and once every three months for boilers.
     Unlike many renewable energy technologies, with biomass you still need to buy fuel.Wood chip boilers are usually cheaper to run than oil or mains gas. Pellet prices vary, but are generally comparable with oil and mains gas. Pellets are usually available in bags or are delivered loose in bulk.
     Planning permission may be required if you need a flue or chimney to be installed or if you live in a conservation area.

Hydro


Hydropower has produced mechanical energy for hundreds of years but was first used to produce electricity in the 1870’s. Most  installations are run of river's (that I have come across). As such, hydro installations in this country are generally dependent upon precipitation and have little impact on their surrounding environment.
     Hydro electricity has the greatest energy yield factor of the renewable technologies meaning the energy it produces in its lifetime greatly exceeds the amount of energy used in its manufacture, operation and eventual disposal. This is due to the reliability and long lifespan of a hydro system. For example, a modest 20kW scheme would save 70 tonnes of CO2 being released into the atmosphere each year from fossil fuelled power stations.

How it works

The power generation from a hydro scheme is dependent upon two variables, the height the water falls, (head) and the volume of water available, (flow). Water is diverted from a given point on a river, ideally near a weir and piped through to a turbine house downstream, where the water falls through a turbine and drives a generator. The water passes through the turbine and returns to the river unpolluted. Various measures are taken to ensure fish are not directed into the channel, which feeds the turbine. These can include mesh screening and electric currents in the water to deter fish from entering. If a hydro scheme is proposed on a fish migratory route, a ‘fish pass’ is built which is designed to guide fish away from the turbine house and up a series of basin-like steps.

Installation

The feasibility of a hydro scheme will depend very much upon the proposed site, as much capital is often spent on civil engineering work such as the weir, water channel and fish pass. A site such as a disused millrace may have an existing weir or water channel and this will reduce the capital per kilowatt outlay.
     Communication with downstream water users is essential to unite support.Fisheries and anglers who use the river can be strong opponents and will seek assurances that their livelihoods or leisure activities will not be harmed.

Wind

                             
Wind is an abundant source of energy. Large-scale wind turbines are now installed around the country and off shore to provide for electricity needs and supplying ‘green’ electricity to consumers from the utility grid.

How it works

For residential sites that have connection to the electricity grid, the cost effectiveness of installing a wind turbine should be carefully examined. In this situation, the annual electricity demand,wind resource and daily demand profile must be considered. If you wish to purchase electricity from a wind turbine, you may be able to sign up to a ‘green electricity’ supply tariff. Small-scale wind turbines range in size from less than 1kW to 50kW. They can be cost effective in off-grid applications and wind power can be more economic than
other renewable options. Energy storage in batteries is necessary in off-grid applications. Large-scale turbines up to 3MW in size,usually installed on windfarms, are generally connected to the grid.

Installation

Wind speed and direction will determine the most suitable position for a wind turbine. Wind speed increases with height, so turbines will give a greater output if placed at a higher level.

Payback and maintenance

Wind turbines have a number of moving parts so annual maintenance is required and your installer can provide this. The payback period of a wind turbine is dependent on utilisation of the electricity generated, which should be off set against that taken from the grid. Payback is therefore highly variable, but could be
as short as 15 years.



CHEERS AND HOPE THIS HELPS!!!!

Friday, 20 April 2012

best radiator ever

I have to admit that this looks like the smartest move forward in traditional central heating since the advent of condensing boilers. I for one will be trying to get my hands on them when they are launched.

Stelrad Radiators has unveiled its new Radical radiator, which is said to offer a 10.5% gas saving compared to a standard heating system, a fact independently confirmed by KIWA. 


Radical comes with a list of benefits: 
• It’s faster to warm up than a standard radiator – the front panel warms up 23% more quickly • Simple and quick to connect – its ¾” male thread connections allow you to connect the pipes directly to the Radical without additional couplers, reducing the risk of leaks and increasing the speed of installation • It comes with an integrated thermostatic valve that can be mounted to the left or right
• It’s fully compatible with renewable energy sources 
• Offers environmentally friendly heating – independently confirmed by KIWA 
• Offers much reduced heat loss into the wall against which it’s mounted 
• It offers comfortable warmth even with low temperature systems such as heat pumps and more quickly – reaching a comfortable temperature up to 8% more quickly 
• It offers higher feelings of comfort from increased radiant heat from the front panel – up to 50% more radiation • It offers lower energy bills – 10.5% lower gas bills are common – and it forces condensing boilers to operate more efficiently 
• It offers time savings both when installing Radical and if you need to drain it Radical is said to be the first ‘serial feed’ radiator on the UK marketplace and the first to come with an integrated thermostatic valve insert. 
Standard radiators are ‘parallel feed’, where the water enters the radiator and is fed via a ‘T’ piece to enter both panels at the same time and the same rate. A serial feed radiator allows the water to enter via a centre tap connection, directing the water flow into the front panel first before, after circulating around the front panel, the water eventually makes its way from the front panel into the back panel. 
Because the front panel of a Radical heats up first, there’s a higher average temperature in the front panel than you get from a standard radiator and less heat is lost from the back panel. 
With Radical, the front panel heats up more quickly than a standard radiator would and ensures the front panel gives off more radiant heat – increasing the feeling of comfort to people in the room. 
The Radical is an ideal companion to lower temperature renewable heating systems, with the return flow from the heating system to the boiler being at a lower temperature, ensuring that the condensing boiler is actually able to condense efficiently. 
It is perfectly suited to both individual and collective heating installations and can be connected to a modulating gas or fuel burner and is combinable with all kinds of low temperature systems such as heat pumps, solar cells and biomass installations. 



Finally the radiator is actually a radiant heater. Brilliant!!

(not paid by stelrad but just think its fantastic!!)

FXNGZ7NGMWM3


Tuesday, 10 April 2012

The Ultimate Guide for Renewable energy in your home!!




Energy is essential to the comfort of our homes, providing space and water heating and electricity. However, there are many ways in the design, construction and operation of our homes of reducing energy needs and meeting those needs with renewable sources, without compromising warmth and comfort.
     Currently, we rely heavily on fossil fuels such as coal, oil, and gas to provide our energy needs. Fossil fuels are non-renewable, that is, they draw on finite resources that will eventually run out. In contrast, renewable energy resources, provided from the sun, wind and water are constantly replenished and will never run out.
     Fossil fuels are also damaging to the environment. They contribute significantly to many of the environmental problems we face today such as greenhouse gases, air pollution, and water and soil contamination - while renewable energy technologies enjoy lower running costs and are clean sources of energy that have a much lower environmental impact.
     Energy is available from a variety of renewable sources appropriate to our homes, including solar, geothermal, biomass, hydro and wind.

Solar Energy

A horizontal surface of 1m2 receives an average of between 1,000 and 1,100 kWh of solar energy per year. This energy is provided by both direct sunlight (40%) and indirect sunlight (60%) and can be harnessed in many ways to heat your home, provide hot water and generate electricity.

Passive Solar Design

Passive solar design is a design approach that maximises the collection of solar heat, minimises heat loss from the building and provides natural ventilation and daylight.
     Unlike active solar heating systems,it doesn't involve the use of mechanical and electrical devices,such as pumps,fans or electrical controls to collect or store the solar heat.Instead energy costs are reduced and the comfort of your house increased by:
• selecting a sheltered location to build on
• constructing a compact building form with high levels of insulation
• positioning the house at an orientation that maximises passive solar heating and
daylight

Direct gain is the simplest passive solar design technique. It necessitates glazing to be concentrated to the south façade and minimised to the north façade.Sunlight enters the house through south-facing windows and is absorbed and stored in the masonry walls and floors.At night, as the room cools, the heat stored in the thermal mass convects and radiates into the room.This maintains a comfortable,even temperature in the home.

A well designed sunspace or conservatory on the south façade can also reduce the heating needs of a house by acting as a solar collector in late spring, summer and early autumn, and by acting as a buffer against heat loss at other times. It is important to choose a high performance glazing, at least double-glazing with a low emmisivity coating, to limit heat loss through glazed areas.However, there are many examples of sunspaces which are poorly designed from an energy point of view and increase heating requirements. Fully glazed conservatories should not be heated and should be separated from the heated space by closeable doors.They should not be regarded as being habitable all year round, as the energy losses from heated
conservatories can negate the energy saved by passive solar collection.
     Passive solar homes can look like any other home, and need not cost any more to build, but they are more comfortable to live in and cost less to run.

Active Solar for Space and Water Heating


Active solar energy systems generally incorporate a roof mounted solar collector,which receives direct and indirect sunlight and changes it into heat. This heat may be used to provide for hot water, or in a combined system, for space and hot water needs. At the end of 2003, approx. 12million m2 of solar thermal collectors were installed in the EU. There is great potential to increase this further.

How it works

Solar collectors can provide 60% of the annual hot water demand of a typical home, depending on the orientation, size, mounted angle and efficiency of the collector. The most common application is for water heating, and 4m2 of solar collector can provide about 80% of hot water needs in summer and 20% in winter (when there is less solar heat available) for a typical family. The solar water system needs to be backed up with a conventional heat source to provide the remainder of the hot water needs such as an electric immersion in the storage cylinder.

Installation in the Home

Solar water heating systems for homes have two main parts: a solar collector and a hot water storage cylinder.
     Typically, a flat-plate collector (a thin, flat, rectangular box with a transparent cover) is mounted on the roof, facing the sun. The sun heats an absorber plate (usually a black metal plate) in the collector,which, in turn, heats the fluid running through pipes within the collector.To move the heated fluid between the collector and the storage cylinder, a system either uses a pump or gravity, as water has a tendency to naturally circulate as it is heated. Systems that use fluids other than water in the collector's pipes usually heat the water by passing it through a coil of tubing in the storage cylinder.
     Evacuated tube collectors can also be used instead of the flat plate. These consist of an array of evacuated glass tubes each containing an absorber tube, which collects solar energy and transfers it to a heat transfer fluid. During the manufacturing process, air is evacuated from the space between the two tubes, forming a vacuum. This vacuum greatly reduces heat loss from the system because there is no air to conduct the heat away. The heat absorbed by the collectors is then transferred to the hot water storage cylinder through a number of heat exchangers. Evacuated tube systems tend to be more efficient than flat plate systems. However, a similar output could be achieved with a flat plate system simply by increasing the area of the collector.
     Ideally, panels need to face directly south. However, a good output can still be achieved between south east and south west.A typical installation will take 2-3 days.
     Today, solar thermal systems are readily available, easy to install and are reliable in operation. Generally systems come with a 5-10 year warranty. A professional installer will advise on an optimised solution for
your specific needs.

Payback and Maintenance

The payback period of a solar water heating system will vary depending on the cost of the fuel you are replacing and the amount of hot water you consume. A typical correctly installed system has a payback period of between 7 and 15 years and little maintenance is necessary.Most systems are run by an electricity-powered pump,which will cost a small amount to run per year.Generally systems come with a 5-10 year warranty and their lifetime is about 25 years.

For a bit more detail on how solar energy can heat your water click here

Active Solar for Electricity


Photovoltaics (PV), which also collect sunlight, are a very different technology to solar water heating,as they use the light to generate electricity.Today,the industry’s production of photovoltaic (PV) modules is growing at approximately 25% annually, and major programs in the U.S.A., Japan and Europe are rapidly accelerating the implementation of PV systems on buildings and connection to electricity grid networks.

How it works

Photovoltaic solar cells, which directly convert sunlight into electricity, are made of semi-conducting materials, such as crystalline silicon.The power output of a PV cell depends on its efficiency and surface area, and is proportional to the intensity of sunlight striking the surface of the cell.
     Groups of PV cells are electrically configured into modules and arrays,which can be used to charge
batteries, operate motors, and to power electrical loads. With the appropriate power conversion equipment, PV systems can produce alternating current (AC) compatible with any conventional appliances, and operate in parallel with and interconnected to the electricity grid network. PV has the great advantages of being silent in operation with a low visual impact making them particularly suitable for urban areas.

There are two general types of PV systems, stand-alone and grid-connected systems:

Stand-Alone Systems

Stand-alone systems produce power independently of the electricity grid network. In some off-the-grid locations, stand-alone photovoltaic systems can be more cost-effective than extending existing power lines.      Direct-coupled systems need no electrical storage because they operate only during daylight hours, but most
systems rely on battery storage so that energy produced during the day can be used at night. Some systems, called hybrid systems, combine solar power with additional power sources such as wind or diesel generators. As well as domestic applications, stand-alone systems can be used to power traffic warnings, parking meters, emergency telephones and buildings in remote locations.

Grid-Connected Systems

Grid-connected photovoltaic systems, supply surplus power back onto the grid and electricity is drawn from the grid at periods when demand in the home exceeds the PV output. Grid-connected systems are generally integrated into the structure of buildings, but can also be ground mounted. These systems remove the need for battery storage. In some cases, utility companies allow additional metering, which allows the owner to sell excess power back to the utility company.

Installation in the Home

A PV array produces power when exposed to sunlight. They can be installed on an existing roof, be an integral part of the roof covering as panels or tiles installed within roof glazing systems or installed on a nearby structure. It is important that nothing casts a shadow over the area where the PV panels will be mounted. PV panels generate more electricity on bright days but do not require direct sunlight, so normal
daylight is sufficient to produce electricity.The ideal orientation for PV panels is south facing, although they still produce around 80% of the optimum output when facing east or west.
     A number of other components are required to properly conduct, control, convert, distribute, and store the energy produced by the array. Depending on the functional and operational requirements of the system, the specific components required, may include major components such as a DC-AC power inverter, battery
bank, system and battery controller, auxiliary energy sources and sometimes the specified electrical load.

Payback and Maintenance

PV is expensive, but with new materials and ongoing product development, it is expected that the price of PV cells will become more competitive in the future. In fact, the price has reduced by one third in the last ten years. Stand-alone systems often provide the most effective solution when grid electricity is not available.      For installations in larger buildings, cost savings are possible when PV panels are integrated in the building design,where they can substitute for other construction materials providing the external skin of a building. Today’s photovoltaic modules are extremely safe and reliable products, with minimal failure rates. Most major manufacturers guarantee the high efficiency operation of their PV modules for 20 or more years, with projected service lifetimes in excess of this. PV panels have no moving parts and require minimum maintenance.

Ground Source Heat Pumps


Ground source heat pumps, also known as geothermal heat pumps, are used for space heating and cooling, as well as water heating. They operate on the fact that the earth beneath the surface remains at a constant temperature throughout the year, and that the ground acts as a heat source in winter and a heat sink in summer. They can be used in both residential and commercial or institutional buildings.

How it works

The earth’s surface acts as a huge solar collector, absorbing radiation from the sun. In most countries the ground maintains a constant temperature between 11°C and 13°C, several metres below the surface. Ground source heat pumps take advantage of this by transferring the heat stored in the earth or in ground water to buildings in winter and the opposite in summer for cooling. Through compression, heat pumps can ‘pump up’heat at low temperature and release it at a higher temperature so that it may be used again. A heat pump looks similar and can perform the same functions as a conventional gas or oil boiler, i.e. space heating and sanitary hot water production. For every unit of electricity used to operate the heat pump, up to four units of heat are generated.Therefore for every unit of electricity used to pump the heat, 3-4 units of heat are produced.

Installation in the Home

The system has three main components:a series of pipes in the ground,a heat pump and a heat distribution system. Lengths of plastic pipes are buried in the ground, either in a borehole or a horizontal trench near the building to be heated or cooled. Fluid, normally water with anti-freeze, absorbs or emits heat to the soil, depending on whether the ambient air is colder or warmer than the soil. In winter, the heat pump removes the heat from the fluid, upgrades it to a higher temperature for use in the building, typically in under-floor heating.
     A distribution system is needed to transfer the heat extracted from the ground by the heat pump.The heat is often in the form of hot water and is distributed around the dwelling by radiators or a low temperature underfloor heating system.

Payback and Maintenance

The initial capital costs of installing a ground source heat pump system is usually higher than other conventional central heating systems. A large proportion of the outlay will be for the purchase and installation of the ground collector.However, the system is among the most energy efficient and cost effective heating and cooling systems available. Typically, four units of heat are generated for every unit of electricity used by the heat pump to deliver it, and the payback is typically about 8- 10 years.The life expectancy of the system is around 20 years. Once installed a heat pump requires very little maintenance and anyone installing a heat pump should speak with their installer regarding a maintenance agreement.

Biomass / Wood


The words biomass or bioenergy are used to describe energy resources derived from organic matter, such as residues from forestry, agriculture and industry, or from purpose grown crops. These resources can be used to provide heat, electricity and transport fuels. It provides about 1% of Ireland’s energy needs in the form of domestic and industrial wood heating. Using wood fuel instead of fossil fuels (oil, coal, gas or peat) makes a positive contribution to the environment. Wood, is a ‘carbon neutral’ fuel. It absorbs as much CO2 when it grows as is released when it burns – a natural cycle.Wood fuel takes just 5-20 years to grow,whereas fossil fuels such as peat and coal were formed over hundreds of thousands of years.
     The main types of wood fuel are chips and pellets.Wood chips are a bulk fuel and, as such, are generally unsuitable for domestic properties. However, they are usually a cheaper fuel than pellets and are appropriate for larger buildings such as offices, public buildings or to heat clusters of domestic properties through a district heating system.Wood pellets are compressed wood,usually sawdust or wood shavings.They are typically 6-12 mm in diameter and 6-20 mm in length. Pellets have the advantage of uniformity in shape and composition, are easy to ignite, are dry, create little ash and will flow freely through feeding mechanisms such as hoppers and augers.These properties make pellets ideal for automatic appliances.
     Wood fuel can be used to create both electricity and heat and is a well established renewable energy source in many countries, including the USA, Sweden,Austria and Denmark.

How it works

Pellets are highly suitable for houses and can be burned in either a boiler or a stove. Pellet boilers provide full central heating and hot water, with a convenience normally associated with oil or gas.
     Stoves provide heating for a single room. Stoves are available in a range of styles, from traditional-looking wood-burning stoves to modern, minimalist designs. Good quality appliances use modern controls to ensure an efficient, clean burning fire. Because they use thermostatic controls and fans to distribute warm air around the room they are safer than traditional stoves,which rely on radiated heat to warm the room, making the room's temperature uneven and the body of the stove dangerously hot.

Installation in the Home

The installation is similar to that of any central heating boiler or stove, and requires a flue and a fresh air supply to be installed for safe and efficient combustion.Many products are programmable to allow you to set the temperature that you require and some can even be controlled by mobile phone remote control.
     Stoves contain an integrated fuel hopper that must be filled manually.Once full, the hopper automatically supplies fuel to the stove, allowing it to operate independently for around 20-40 hours. For boilers or larger systems which require a greater fuel input, you may decide to site your storage facility adjacent to the boiler, and install a completely automatic fuel feed system, such as an auger, so that you do not have to re-fill the hopper manually. Fuel storage is an important consideration as pellets are a bulky fuel, requiring about three times the storage space of oil. However this requirement could be met with more frequent deliveries. The store must also be kept completely dry as pellets disintegrate on contact with water.

Payback and Maintenance

Maintenance is similar to that of conventional stoves and boilers. The ash pans of both stoves and boilers will require emptying, typically once per month for stoves and once every three months for boilers.
     Unlike many renewable energy technologies, with biomass you still need to buy fuel.Wood chip boilers are usually cheaper to run than oil or mains gas. Pellet prices vary, but are generally comparable with oil and mains gas. Pellets are usually available in bags or are delivered loose in bulk.
     Planning permission may be required if you need a flue or chimney to be installed or if you live in a conservation area.

Hydro


Hydropower has produced mechanical energy for hundreds of years but was first used to produce electricity in the 1870’s. Most  installations are run of river's (that I have come across). As such, hydro installations in this country are generally dependent upon precipitation and have little impact on their surrounding environment.
     Hydro electricity has the greatest energy yield factor of the renewable technologies meaning the energy it produces in its lifetime greatly exceeds the amount of energy used in its manufacture, operation and eventual disposal. This is due to the reliability and long lifespan of a hydro system. For example, a modest 20kW scheme would save 70 tonnes of CO2 being released into the atmosphere each year from fossil fuelled power stations.

How it works

The power generation from a hydro scheme is dependent upon two variables, the height the water falls, (head) and the volume of water available, (flow). Water is diverted from a given point on a river, ideally near a weir and piped through to a turbine house downstream, where the water falls through a turbine and drives a generator. The water passes through the turbine and returns to the river unpolluted. Various measures are taken to ensure fish are not directed into the channel, which feeds the turbine. These can include mesh screening and electric currents in the water to deter fish from entering. If a hydro scheme is proposed on a fish migratory route, a ‘fish pass’ is built which is designed to guide fish away from the turbine house and up a series of basin-like steps.

Installation

The feasibility of a hydro scheme will depend very much upon the proposed site, as much capital is often spent on civil engineering work such as the weir, water channel and fish pass. A site such as a disused millrace may have an existing weir or water channel and this will reduce the capital per kilowatt outlay.
     Communication with downstream water users is essential to unite support.Fisheries and anglers who use the river can be strong opponents and will seek assurances that their livelihoods or leisure activities will not be harmed.

Wind

                             
Wind is an abundant source of energy. Large-scale wind turbines are now installed around the country and off shore to provide for electricity needs and supplying ‘green’ electricity to consumers from the utility grid.

How it works

For residential sites that have connection to the electricity grid, the cost effectiveness of installing a wind turbine should be carefully examined. In this situation, the annual electricity demand,wind resource and daily demand profile must be considered. If you wish to purchase electricity from a wind turbine, you may be able to sign up to a ‘green electricity’ supply tariff. Small-scale wind turbines range in size from less than 1kW to 50kW. They can be cost effective in off-grid applications and wind power can be more economic than
other renewable options. Energy storage in batteries is necessary in off-grid applications. Large-scale turbines up to 3MW in size,usually installed on windfarms, are generally connected to the grid.

Installation

Wind speed and direction will determine the most suitable position for a wind turbine. Wind speed increases with height, so turbines will give a greater output if placed at a higher level.

Payback and maintenance

Wind turbines have a number of moving parts so annual maintenance is required and your installer can provide this. The payback period of a wind turbine is dependent on utilisation of the electricity generated, which should be off set against that taken from the grid. Payback is therefore highly variable, but could be
as short as 15 years.

Thursday, 5 April 2012

Heating advice and tips


This blog is designed to give you clear, impartial advice about how best to maximize the efficiency of your home heating system, whether a new build or a retrofit. It will show you how to do this in ways that are cost effective, sustainable and environmentally friendly.

( But be warned it has tired me out typing it, i think its a long one!!)

It examines the practical ideas and the various heating technologies you should consider for your home and offers clear, concise advice.

Home is where the hearth is
We live in a world of ever growing energy-awareness. Increasing home heating costs driven by fluctuating fuel prices mean we must try to use energy as efficiently and sustainably as possible, without compromising the comfort of our homes, workplaces and public buildings. The aim of this blog is to give householders an informative guide to the various home heating systems available, and their relative merits.

 Perhaps you want to improve the efficiency of your existing heating system? Or maybe you wish to learn about the most up to date home heating technologies? If so, this blog will (hopefully :-)) give you a clear guide on how to create warmth and comfort in your home, in ways that will help the environment and your pocket.

Wrap up well

Before examining your heating system, it is important to review how well your house is insulated. For example, fitting draught excluder's around windows and doors, where no draught protection is in place, can cut heat loss by as much as 20% in winter.
     Investing in high-grade insulation does more than cut down on heat loss. It also means that once your home is heated to the required temperature, it is easier for your heating system to maintain this temperature, so it uses less energy. Insulating your home can give long term benefits through reduced running costs. The amount you spend initially on your heating system will also be reduced, as a smaller, more efficient heating unit will be required.

To find out how to insulate your attic, click here.

Fuel – choose the sustainable option

There are a number of factors to consider when selecting the type of fuel for your home. Like availability, storage and cost all have to be taken into account. But just as important are the environmental impacts your choice of fuel will have.
     Most of the energy we use in Ireland comes from fossil fuels - oil, coal, peat and gas. These are not renewable – once they are gone, they cannot be replenished. Burning fossil fuels releases carbon dioxide (CO2) into the atmosphere. This is a major contributor to climate change.

The sustainable alternative to fossil fuels is renewable energy and this will never be exhausted. Renewable energy is available to us in many forms. The main ones are:

  • Solar energy (the sun) – for space and water heating;
  • Geothermal (heat from below the surface of the earth) – heat pumps for space and water heating;
  • Biomass (woodchip and pellets) – boilers and stoves for space and water heating;
  • Wind powered turbines (the wind) – for electricity generation;
  • Hydro-electric power (moving water in streams) – for electricity generation.


Heat – meet your annual heat demand

The total amount of heat required for a dwelling is called its Annual Heat Demand. This is a factor of:
Heat lost from inside to outside through the roof, windows, doors and walls; Heat required to offset the loss of warm air escaping through windows, doors,chimneys and other openings and heat to warm up the cold fresh air that replaces the lost air and provides ventilation; Heat required to provide adequate hot water; and Free heat from the sun, from occupants and household appliances.
   
The Annual Heat Demand for a house will determine the required power output of the heat generator to be installed. It can be met from two main types of heating systems:
 Central heating systems: oil, gas, solid fuel (coal or biomass) or biomass boilers, or heat pumps are used to heat water or air and distribute it throughout the house in pipes or ducts;
 Localised heaters: open fires, electric heaters, closed gas fires or stoves are used to provide heating and, where equipped with a back boiler, hot water.

The types of central heating generators available to deliver the Annual Heat Demand for your home are detailed in the further on.

Practical advice for heating systems in new homes

There are a number of areas where you can optimise the heating system when you are building your new home. These will help to minimise the load on the heating system, and ensure it operates as efficiently as possible over the building life-cycle.

Site and design the most sustainable building possible

Locate the living areas to the southern aspect, so that most use can be made of available light and solar energy. Also, shelter the building from the external elements in a suitable manner.

Ensure the building is insulated and sealed efficiently

Ensure the building is insulated to as high a specification as possible. The minimum I would like is air permeability of 10m3/m2/h. Best Practice is considered to be 5m3/m2/h. Air tightness should also be
discussed with your building contractor to ensure that good construction practices
are used during the build.

Size and select the most efficient heat generation system possible

Take energy efficient designs into consideration in sizing the most efficient heat generation system for the dwelling.Also balance long-term running costs against short-term savings.

Select the most efficient and practical heat emission system

Make sure the heat emission system, be it radiators or underfloor heating, is as efficient as possible, taking
into consideration the type and location of units specified. Find out the difference between the two here.

Ensure efficient control of both space heating and Domestic Hot Water (DHW)

Make sure that once the most efficient heating system has been chosen, good control systems are also employed. Click here to find out the importance of controlling your system!!

Practical advice for heating systems in existing homes

There are a number of areas where you can optimise the performance of your heating system when renovating your home, or replacing an existing heating system:

Ensure the building is insulated, sealed and draught-proofed

There is little point in incorporating the most energy efficient generation and distribution system, if the building is leaky and not insulated - allowing the unrestricted flow of energy from the dwelling. A poorly insulated house could be losing up to 30% of its heat through its roof alone – costing you money and contributing to global warming.

Ensure the heating system is in good working order

Ensure the good performance of your heating system through regular maintenance via a qualified boiler service engineer. Click here to find out why you should get your heating serviced and how much you could save!!

Replace defective equipment with an energy efficient and/or renewable technology alternative

Only once the building fabric and ventilation heat loss have been minimised, and you are sure the current heating system is operating inefficiently, should investment in a new technology be considered.

Ensure system control is as efficient as possible

Make sure your present control system operates efficiently, and if possible, enhance it in line with the suggestions in this blog.

Renewable heat generation options – the sustainable alternative

We are rapidly depleting our supplies of non-renewable energy (oil, gas, coal and peat). We also need to reduce our emissions of greenhouse gases. This means it makes sense to adopt sustainable energy solutions wherever possible.
The good news is that there now are a range of efficient renewable energy technologies we can use to heat our homes. These energy systems include:

  •  Solar energy
  •  Biomass systems
  •  Heat pump systems

We shall examine each of these technologies in more detail:

Solar energy

Even in a moderate/cold temperate climate, solar energy can still contribute significantly to your domestic heating requirements. Current technology allows heat to be gained in a passive or active way.

Passive solar energy
Passive solar energy involves capturing heat from the sun via windows and other glazed surfaces. Modest levels of passive solar heating can reduce building auxiliary heating requirements from 5% to 25%. Planning the use of passive solar heating can reduce heating energy use from between 25% to 75% compared to a typical structure. Glazing should be concentrated on the south façade to make best use of solar energy (windows on the north façade should be minimised to limit heat loss). Passive solar energy can also take advantage of the thermal mass of building materials, such as masonry walls or concrete floors. These can absorb and store energy during the day and release it gradually during the evening.
However, south-facing glazed areas should not be increased too dramatically. Otherwise additional measures will be required to avoid overheating in summer and excessive heat loss at night and on overcast days in winter.

Active solar energy
Active solar energy systems use solar collectors positioned on south-facing roofs to harvest heat from the sun and distribute it using an air or water network. Solar systems can provide on average 60% of a family’s annual hot water requirement. Solar heating is best contemplated when building a new house. However, while retrofitting of an existing house can be difficult and expensive, convenient solar heating ‘packages’ are now available which can produce a sizeable volume of a typical house’s annual hot water demand. Click here to find out how Solar heats your water!!
However, whether new or retrofit, a cost analysis of solar heating systems should be completed prior to installation, in order to determine the possible payback period on investment based on operational cost saving.

Biomass systems
Biomass boilers burn wood from managed forests to produce hot water for heating and domestic use. The wood matter is chipped or compacted into small pellets of uniform size and moisture content. Some models offer up to 90% efficiency. Chips are slightly less energy efficient but are cheaper to buy. Biomass boilers can be fully automatic once installed. In order to keep them topped up with fuel, some boilers have special ‘hoppers’ (storage tanks) which provide enough fuel for months of operation. Capacities of up to three tonnes are typical and this may last the average dwelling for a year. Storage conditions of the chips/pellets are important, as their moisture content affects the efficiency of the boiler. Chips and pellets produce ash after burning. This can be easily removed and (spread in the garden as it contains nutrients :-)).
Pellets and wood chips are bulky products and do require a lot of storage area. This should be a consideration in your decision. Typically an average year’s supply of pellets (3 tonnes) will need at least 6m3 of storage volume, while wood chips (approximately 4.5 – 5 tonnes) will require between 8 and 10m3.

Heat pump systems
Heat pumps release heat that is stored in air, ground or water and make it usable for domestic heating applications. Although they have higher installation costs than conventional fossil fuel heating systems, heat pump systems offer a very energy-efficient way of providing heat. As heat pumps typically exploit low grade temperature sources, they will be more efficient when supplying heat to low temperature emitters (e.g. under floor heating, low temperature / large area radiators). It is also very important that the house is very well insulated and draught-proofed. You will need to ensure that this is the case if you areconsidering using these systems in an existing house.
Heat pumps exploit their heat sources in one of two ways:
Open systems
Water from vertical boreholes, rivers, streams, lakes, etc. is pumped up into the heat pump where useful energy is transferred to the heating system water, and the extracted water is then pumped back into the ground.
Closed systems
These use a loop of buried plastic pipe as a heat exchanger. They are particularly appropriate for underfloor heating in a house, as the typical distribution temperature is 30ºC to 40ºC.

Air source heat pumps
Air source heat pumps heat the interior of a building using air from the outside. There are two types of air-source heating systems.
Air-to-air systems provide warm air, which is circulated to heat the building.
Air-to-wate rheat water to heat a building through radiators or an underfloor system.

Ground source heat pumps
Energy from the sun is stored in the soil. As the heat pump system extracts this energy, the sun constantly tops it up to maintain a constant temperature all year round. Heat is extracted from pipes buried horizontally or vertically in the soil, a metre or more deep to ensure that frost cannot damage them. The ground above the pipes cannot be planted with large trees or shrubs and care must be taken to ensure it is used in a manner which does not adversely affect the piping system. A geo-thermal heating system may be used if the dwelling has a large enough area with a suitable soil type around it.

Water source heat pumps
Where there is a sufficiently large body of ground water available close to a house, it may be used as a heat source, using either an open or closed system.


Choosing your conventional space heating system

Conventional boiler
Gas, oil or solid fuel boilers, located inside or outside the house, heat water which is then distributed by pump or gravity circulation to heat emitters (radiators) in each room. New boilers can achieve good efficiencies (minimum seasonal efficiency of 86%) when installed, commissioned and serviced effectively. Distribution pipes for all boilers should be well insulated and waterproofed to minimise heat loss.

Condensing boiler
Condensing boilers burn gas or oil and condense their flue gases to achieve efficiencies of 91% or higher. Although more expensive than conventional boilers, their lower running costs mean the price difference will be recovered over the boiler’s lifetime. They emit a harmless plume of water vapour to the atmosphere during operation. Click here to find out how they work!!

Cooker and boiler
Suitable for large kitchens, these appliances burn solid fuel, oil or gas to provide cooking ovens and to supply hot water for heating. When using solid fuel, the flue/chimney should be cleaned twice annually and the appliance itself should be cleaned as often as twice weekly, particularly if bituminous (i.e non-smokeless) coal is used. This type of coal produces a lot of slag deposits when burnt. These can stick to the boiler surfaces and reduce efficiency.

Back boiler
Open fires are very inefficient, perhaps as low as 20%, with most heat being lost up the chimney stack. By trapping more of the fire’s heat energy and using it to provide domestic hot water and space heating, a high output back boiler increases the efficiency to approximately 40–50%. Solid fuel back boilers must be cleaned frequently (as often as twice weekly).

Open fires
Solid fuel and gas open fires, while a visually attractive form of heating for Irish homes, are extremely inefficient. Typically they offer only 15% to 20% efficiency, meaning that up to 80% of the heat literally goes up the chimney. Open fires require air for combustion, and cause an increased ventilation rate in rooms. Draughts can be avoided if the air supply is located close to the fire, (e.g. ducted in directly from outside). A damper that closes the chimney when not in use will help to avoid unnecessary heat loss. Fully sealed gas fuelled fires with back boilers offer an alternative to open fires.

Click here to find out the benefits of solid fuel stoves!!

Choosing your water heating system

Systems for meeting Domestic Hot Water demand (DHW) fall into three main types:

  1. Centrally stored systems – these store hot water in a cylinder, tank or thermal store
  2. Locally stored systems – these store hot water for a specific appliance
  3. Instantaneous water heating – these heat water when it is required

Centrally stored systems

Boiler systems
The central boiler heats water in a hot water storage vessel such as a cylinder or thermal store. The hot water is then distributed to the taps on demand as required. There will be heat losses from the cylinder / storage vessel from the hot water stored there, and it is recommend to lag or insulate this as much as possible to minimise this loss.There is also some heat loss through the primary pipework from the boiler to the hot water storage vessel.

Room heater systems
Heat exchanger in the room heating unit, such as a back boiler in an open fire, heats water for domestic use. This system incurs both storage and distribution losses. These should both be minimised to enhance system performance.

Immersion heater systems
These systems use the electric heating elements installed in hot water storage cylinders. These typically have two electric elements: (i) a low rated element to supply small quantities of hot water for sinks or showers, and (ii) a higher rating element to heat sufficient water for larger demands, such as baths.

Locally stored systems

Larger storage type
A range of gas fired or electric wall or floor mounted domestic water storage heaters are available for baths and multi-outlet applications.

Over-sink type
Gas fired or electric hot water storage heaters of this type are available for single outlet sinks or basins.

Under-sink type
Electric under-sink hot water storage heaters are available for single outlet applications and work in much the same way as over-sink types.

Instantaneous systems

Gas fired instantaneous water heater
A suitable natural or liquid petroleum gas supply and a minimum water supply pressure of 1 bar or 10 metre head is required to operate this type of water heater.

Electric instantaneous water heater
An electricity supply of 30 amps and a minimum water supply pressure are required to operate this type of water heater.


Heat distribution systems – the options

Once generated, heat is distributed throughout the house by means of water or air, using a network of pipes or ducts.

Water distribution

Hot water from a boiler is pumped around a circuit to the heat emitters/radiators at a required flow rate to meet the heating demands. The water circuit may be open or closedto the atmosphere:

Open systems
Open systems (e.g. solid fuel systems) use a small feed and expansion tank located in the attic to fill the system and to allow for the expansion of water during the heating process. A vent pipe from the heat generator provides a safety outlet in the event of water boiling.

Closed systems
These systems are closed to the atmosphere (pressurised systems), which means they can operate at slightly higher temperatures than open systems. Closed systems must incorporate a small expansion tank and air safety release valve. The system is filled by an automatic valve instead of a feed tank.

Air distribution

Warm air generators
Use ducting to distribute heat throughout a dwelling. Ducting is usually made of metal and is hidden in the ceiling void. Warm air systems are particularly suitable for thermally lightweight buildings, i.e. buildings in which the walls floors and ceilings of the rooms are constructed of plasterboard or timber.

Warm air recovery systems
These systems incorporate a ventilation system and an air-to-air heat exchanger in the attic space. They are designed to work in conjunction with passive solar design and heat recovery ventilation in newer, more sustainably designed homes.

Heat emitters – the options

Heat gets into your room via a heat emitter. They fall into three distinct types:

  1. Centrally generated heat emitters
  2. Underfloor heating
  3. Localised heat emitters

All types offer advantages and disadvantages, which are examined in turn.

Radiators 

Radiators are flat, sealed metal containers through which hot water flows from the heat generator e.g. boiler or heat pump. They normally operate at temperatures of between 60º and 65ºC (depending on the boiler thermostat setting). However, low temperature radiators are available for use in conjunction with heatpump or condensing boiler systems.
Advantages of radiators:

  • Fast response (heating up) time
  • Can be situated near cold surfaces, e.g. single glazed windows, thus reducing down-draughts
  • Individual room control possible using TRVs
  • Relatively low installation costs
  • Retrofit possible in older homes

Disadvantages of radiators:

  • Subject to leaks and require maintenance
  • Some systems (condensing boiler/geothermal heat pump) require larger radiators to operate efficiently
  • Can create uneven heating, particularly in larger rooms
  • Unsightly and interfere with positioning of furniture


Underfloor heating

This is a means of distributing heat throughout a home via a network of hot water pipes built into the floor, through which flows heated water.
Advantages of underfloor heating:

  • No radiators, so easier decoration and improved room appearance
  • Lower temperature, radiant heat provides a stable comfortable environment
  • Provides a background level of heating
  • Ideal for use with heat pumps or condensing boilers
  • More uniform heat distribution throughout the room
  • Intelligent/self-learning controls can improve response times

Disadvantages of underfloor heating:

  • Up to 20–25% more expensive to install
  • Slow response time is less suited to the Irish climate
  • Controls and design must be of high standard to ensure satisfactory operation
  • Limited flexibility – considerable building work is required to change the system
  • Room furniture may impede the emission of heat from floors
  • Low temperature surface of floor may be inadequate to heat poorly insulated spaces
  • Generally only appropriate for new homes/new buildings
  • Need higher levels of insulation in the floor than for conventional building.


Localised heat emitters (room heaters)

These are heat emitters which generate and emit heat into the space they occupy, independent of a central heating system. The main types are:

Wood pellet/solid wood stoves
A wood burning stove can easily power many radiators as well as providing hot water.

Gas or oil fired room heaters
operate at 100% efficiency by burning LPG or kerosene, but release CO2 and water vapour, so require adequate ventilation.

Electric heaters
radiant, blow heaters, convectors, oil filled radiators and storage heaters. Costly, but nearly 100% efficient

Open Fires
visually attractive but highly inefficient form of heating (only 15-20% in terms of heat output).

Enclosed gas fires
Aesthetically pleasing and highly efficient, with no draught effect.

Advantages of localised heat emitters

  • Provide instant and convenient heat
  • No distribution network required
  • Can be very efficient, depending on type used
  • Can provide a quick, reliable and cost-effective heating solution

Disadvantages of localised heat emitters

  • Some use non-sustainable fuels. Greenhouse gas emissions much higher compared to alternative energy sources.
  • No storage capacity
  • May pose a safety risk
  • Controls limited
  • Usually have little or no water heating facility


Control systems – take charge of your heating

(This is where i sound like a dick)
Whether it is for a new build, or the upgrade of an existing system, as many as possible of the relevant energy saving control measures shown in this blog should be included. By implementing these measures, you will not only reduce your heating bill, but also reduce the carbon footprint of your home.

This section will examine the four key areas where control measures can be implemented to improve the efficacy of your home heating system:

  • Control of the heat generator
  • Control of the heat distribution system
  • Control of the heat emitters
  • Control of the hot water system


Control of the heat generator

Where economically viable, as many as possible of the following control options should be included for the efficient and safe operation of a fuel burning heat generator.
Time switch
A time switch enables the boiler to provide heat to either the space heating and/or the domestic hot water supply circuits when required. This means, for example, that domestic hot water can be provided in the summer when heating is not required.
Delayed start thermostat
This control device uses a time switch to monitor internal and external temperatures and delays the boiler start. In this way, it reduces the number of hours per day that the heating system runs, without creating any discomfort.
Programmer
This device controls both the space and water heating systems, allowing you to choose when you want the system to operate (usually on a daily/weekly schedule).
There are three types of programmers, offering varying degrees of control.

  1. A mini-programmer which allows (i) space heating and hot water to be provided simultaneously, or (ii) hot water alone, but not space heating alone.
  2. A standard programmer which uses the same time settings for space heating and hot water.
  3. A full programmer which allows the time settings for space heating and hot water to be fully independent.

Programmable room thermostat
This device combines a time-switch and room thermostat and allows you to set different time periods with different target temperatures for space heating.
Boiler interlock
This is an arrangement of the system controls which your electrician can undertake to ensure that the boiler does not fire when there is no heat demand.


Control of the heat distribution system

Distributing heat efficiently around your home is just as important as generating it efficiently. This section discusses the options available for controlling the distribution of heat.
Zone control
Dividing the heating system into separate zones allows it to operate independently in different parts of your house. Typical zones might be (i) the living room, (ii) the rest of the ground floor, (iii) the first floor, and (iv) the domestic hot water storage cylinder. Each zone will be switched on only at the times when there is a demand for heat in that area. All heating systems should have a separate hot water circuit to allow for the heating of hot water without needlessly heating the home.
Load compensator
This device regulates the water temperature in the DHW circuit in direct relation to the temperature measured inside the dwelling.
Weather compensator
Designed for larger installations, a weather compensator control helps reduce energy use and associated utility costs by linking the temperature inside a dwelling to that outside. This means, for example, that when outside temperatures rise, the demand for space heating in the house is reduced, thus saving on heating costs. Weather compensation is particularly beneficial in conjunction with condensing boiler systems as it can help the boiler run more efficiently for longer.
Boiler energy manager
This device improves boiler control by using a selection of features previously detailed, such as load and weather compensation, boiler interlock, zone control, etc. It is an extremely efficient way to operate the heating system in your home.
Flow switch
A flow switch detects when there is no water flow through the Domestic Hot Water (DHW) system, for example, when all TRVs are in the fully closed position and there is no heating
requirement.

Control of heat emitters

Water is the most common distribution medium in heating systems and heat is generally emitted to rooms via radiators or convectors (fan assisted radiators). When heating is not required in a particular part of your home, you can isolate heat emitters in this area either manually or automatically.

Manual control
Most radiators and convectors are fitted with a hand wheel valve. This is essentially an on-off switch which allows the heat emitter to be isolated from the heating circuit.

Thermostatic Radiator Valves (TRVs)
A thermostatic radiator valve (TRV) may be installed instead of the hand wheel valve. The TRV has a number of settings which adjust the flow of heating water to the heat emitter, according to the temperature of the room. So, for example, in rooms where a high level of heating is required, the TRV will be set at the top setting. Conversely, if only background heating is desired, then the valve will be at its lowest setting. A motorised valve may be used along with the hand wheel valve. It is activated by a thermostat located in the room. However, while motorised valves may offer more effective heat control than a conventional TRV, they are also more expensive.

Control of the hot water system

As has been previously outlined, domestic hot water supply may be provided from a central storage cylinder, from local storage or from an instantaneous source. There is scope for energy saving in the way hot water is produced and used.

Control of central storage cylinder
The hot water cylinder should be supplied with heating water from the boiler via a separate circuit from the space heating circuits. Two aspects of a hot water cylinder that should be controlled are (i) the times that heating water is circulated from the boiler to the coil heat exchanger and (ii) the temperature at which the hot water in the cylinder is stored.

Point of use control
It is recommended that domestic hot water should be stored at 60ºC. However, water at this temperature is too hot for showers. The process of mixing hot water from the storage cylinder with cold water from the cold water cistern can be automated by installing a Thermostatic Mixing Valve. Once set at the desired temperature, the shower water temperature always remains the same, provided the water in the storage cylinder is at or above the desired temperature. This minimises energy and water wastage.


Instantaneous DHW at isolated users
In large houses, distributing heat energy and water from a central storage cylinder causes wastage. Installing a local hot water system at points of usage eliminates this waste. Local systems may be either (i) storage or (ii) instantaneous. They use natural gas, liquid petroleum gas or electricity.

Problem solving

Heat generation and distribution systems are prone to a number of issues which can affect their performance. It is therefore recommended that your heating system is serviced regularly.


Maintenance
An annual boiler safety check and boiler service, carried out by a professional service engineer ensures that your boiler is functioning properly. If your oil or gas boiler hasn't been serviced recently, then you could be wasting money. In fact, by servicing your boiler, you could improve your overall efficiency by 10%.
The benefits of servicing your boiler

  • Saves you money - reducing your heating costs
  • Reduces CO2 emissions - benefiting the environment
  • Gives you peace of mind - improving your boiler’s reliability and safety

All heating systems including those fuelled by renewable energy will perform more efficiently, and therefore more economically, if they are well maintained and serviced on a regular basis. Your system will come with a user’s manual and a service schedule. These are set out by the manufacturer and we would recommend that you follow these to ensure that your heating system works at its optimum level all the time.

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