• Sustainable Solutions

 

Sustainable solutions

At present there is a growing awareness in the need for our homes and communities to be more conscious of our energy consumption and how that energy is produced. With rises in the price of gas and electricity inevitable, our bills and the cost of running our home grows, it seems that we  have little choice but to reduce our demand on natural resources and start to turn our attention to making our homes more energy efficient, and in some respects self sufficient.

At Homes in Harmony, we can offer advice on the best solution for your home. Simply contact us to discuss your requirements. 

Types of Sustainable solutions
There are a wide range of products on the market which offer various solutions for domestic space heating; from solar thermal, the various heat recovery systems, under floor heating be either electrical or wet (hot water), wood chip boilers, biomass and dual fuel heaters.
 
Similarly there is a growing diversity of Micro Generation systems that enable us to partially or fully produce our own electricity, this can not only reduce the amount of energy we use from the  Nation Grid and  in some cases actually get paid for the excess energy they produce, especially with the feed in tariff to be introduced in 2010. Wind turbines, photovoltaic cells, combined heat and power systems (CHP- produces not only heating but also electricity) and hydro generation which is naturally dependent upon locality. 
 
Water collection and recycling is another key feature of sustainability, every time we flush the toilet we use 8litres of water. The average water consumption per day for washing and cooking is nearly 150litres per person. With growing pressure from population increase and global warming, water is becoming a major resource. Taking into consideration the energy used in the distribution and purification of water which is a forgotten issue. With 1% of our total green house gas emissions in the UK, come from pumping and treatment of water and sewage.
 
Below you will find a brief introduction into the various systems, how they work, approximate costing, performance and their sustainability, please click on a link or simply scroll down.

Heat Recovery (GSHP, Air to air, Air to water)   Wood_chip_boilers   Biomass   Photovoltaics  Wind_turbines

Solar heating

How it works
Solar thermal uses the sun’s rays to heat a series of tubes or collectors by radiation (meaning it will still work on a cloudy day). This energy is then transferred by a liquid be either normal water or a liquid similar to anti-freeze, which is pumped through the system and then stored in a hot water storage vessel (HWSV). Solar heating is generally mounted on roofs be they pitched or flat, and occasionally even to vertical walls. In the UK solar thermal is normally used in conjunction with a secondary heating system such as a gas boiler. 
 
Benefits
Solar energy is free to all, and solar heating will provide nearly all of your hot water needs during the summer and less during the winter months, however on a whole, solar thermal will provide nearly 60% of your hot water needs for the year. This however is dependent on system type and how energy efficient the property.

A Vaccum tube solar thermal installed on a roof.

Downside
Solar heating peaks during the summer months when we tend to use less hot water. Maintenance is required between 3-5 years; this would incur extra costs depending upon the access to the roof. The compatibility of the properties current heating system with solar thermal could possibly result in purchasing a new boiler and HWSV increasing the cost of installation. The system requires a pump which uses energy, however little. (note check with mis3001 as to the use of bypass valves with combi boilers)

Types
There are 2 main types of solar heating collectors; flat plate and vacuum tube. Flat plates are not as efficient as vacuum tubes and require twice the surface area, also they only generate their peak performance during the summer months and very little if any in winter. Flat plate tubes lose any heat gains in colder ambient air temperatures, windy conditions and the evaporation of moisture from its surface. They are cheaper than vacuum tubes and the units are slimmer and more aesthetically pleasing.

In vacuum tubes the heat collectors are encased in a vacuum, like thermos flasks. Heat cannot penetrate a vacuum and therefore heat loss is minimal so they can operate in colder, windy and cloudier conditions. Due to the efficiency, the area covered by the system installed on the roof is smaller; with the smaller size the heat collected is transferred quicker to the heat store and thus responds faster. Another important feature is that there is the elimination of condensation, moisture and contaminants of the tubes providing easier maintenance and all year round performance.
 
Considerations
• Any roof/s that are south facing? 90 degrees of south is acceptable.
• Is the roof area shaded? or partially shaded? Any shading will reduce the efficiency.
• The pitch of the roof nominally 20—50 degrees.
• Structural integrity of the roof – will the roof take the imposed load of the unit?
• What is the demand for hot water – how many people live in the house?
• Type of system used either flat plate or vacuum tube collectors – in the UK Vacuum tube are more energy efficient.
• Type of heating system in place already, some boilers will not work with solar heating, although there are products to get round this.
• Cost of the installation?
• Will Planning approval be required?
• Maintenance of the system – will a scaffold be required to gain access to the roof?
 
Costing
A standard unit for a small family is approx £3,000 - £6,000. Maintenance costs vary depending upon access.

Sustainability
With the main components being copper and glass, which have less embodied Co2 than say aluminium, the only main question is where the panels are made and the transport inherited Co2, more so if coming from overseas. On the whole this is outweighed by the energy saving gained from solar thermal with nearly 650Kg of Co2 being reduced a year. back_to_top

Heat Recovery Systems

How it works
There are several types of heat recovery systems; ground source heat pumps (GSHP) are becoming quite well known whilst air to water and air to air heat pumps are lesser known. Some use the recovered heat to help preheat a Hot Water Storage Vessel (HWSV), some use the heat via an exchanger to warm incoming fresh air at comfortable temperatures. The principle for heat extraction systems all work in a very similar fashion; the extraction of heat from ground or air, and then to distribute this heat around the property.

Benefits
Like solar thermal, the majority of heat recovery systems can reduce the demand on space heating. They can provide nearly all of the space heating requirements, but again that is dependent upon the energy efficiency of the property.

 

A ground source heat pump, with underfloor heating and supplimentary heating from a boiler.

Downside
Better suited to new build or complete renovation, heat recovery systems require substantial investment and symbiosis within the home. Whether that is the installation of ducting and ventilation systems, laying of under floor heating pipes or digging trenches in the back garden, it is difficult to adapt an existing building but not impossible.

Generally they produce lower temperatures than solar thermal and are often incorporated with under floor heating – which operates at lower temperatures of around 20 – 30 degrees Celsius. With average heat collected around 20 degrees Celsius.

All the heat recovery systems require pumps and motors of some description, although these are generally low amperage and have minimal energy needs they still require this energy for operation. In quite situations the back ground noise of the motors can become evident.

With GSHP the amount of plastic pipe that is required to capture the heat from the ground can be quite substantial, the amount of heat to be collected from the energy demands of the occupants can result in 30 – 50 meters of plastic pipe buried in the garden, even though generally HDPE is used as it is more environmentally friendly than PVC as it can be recycled and contains significantly less hazardous chemicals than PVC. One cannot escape the fact that it relies heavily upon petro chemicals in its manufacture.

Some systems also use antifreeze agents to help absorb as much heat as possible as the solution gets slowly pumped around, if there was a problem with the system and it leaked, the antifreeze would contaminate the ground water.

Most ventilation ducting is manufactured from aluminium, which has one of the highest embodied Co2 of any material, due to the intense heat required for smelting and purification. Although recycled aluminium is considerably less.  This can drastically reduce the energy saving from the heat recovery system and the overall environmental impact.

Maintenance cost vary and nominally the system requires an inspection once a year.

Types
Ground Source Heat Pumps as mentioned are the most common type and has received quite a lot of attention. At a depth of 1.5 meters the earth remains at a constant temperature and is not affected by ground frost or excessive heat. GSHP are solar thermal systems, and not geothermal. The system requires a large garden where a long trench is dug and looping coil of HDPE pipe work is laid and then buried, or if space is limited a bore hole drilled to the depth of up to 30meters, a stainless steel frame to which the pipe work is attached and lowered into the hole and then filled. HDPE has a life span of about 100years and is both flexible and durable. Both are expensive to install but can produce nearly all of your space heating requirements in a highly insulated building.

Air to Water Heat Recovery
Air to water systems are a compact unit and require limited outside space, they take the ambient outside air temperature and then use this in a manner similar to a refrigeration unit to extract the heat and store this in a HWSV. They can also produce nearly all of a new builds space heating demands and cost substantially less than GSHP.

Air to Air Heat Recycling
Using a ventilation system that extracts air from inside the property, it transfers this through a heat exchanger so as the fresh air being drawn over this so that warm air is then supplied around the property. Again in a new build or renovation it can supply all the needs for space heating.

Considerations
• Choosing the appropriate system for your property
• The space heating demands of the property
• Cost of installation
• Maintenance costs

Cost
Depending upon the system, unit costs of between £8,000 -£20,000 can be expected.

Sustainability
This is a were the systems encounter problems, as mentioned before, GSHP use 10’s of meters in HDPE which is a petro chemical product, some types use an antifreeze which if leaks could pollute the ground water. Likewise with an air to air system that uses aluminium ducting for the heating and ventilation the embodied Co2 is very large.

In all the systems a pump or motor is required for them to work and this uses energy, some will use more energy than others. On the whole GSHP can save many tonnes of Co2 a year were as air to water and air to air can save nearly 1 tonne.  Some systems are manufactured in the UK which limits transport issues. Taking everything into account all the systems seem a viable option with minimal maintenance and big savings in Co2. GSHP or other heat recovery systems are very well suited to new build properties with high levels of insulation, although an Eco refurbishment can also benefit. back_to_top

Wood Chip Boilers

How it works
Wood chip boilers use a compressed pellet of saw dust which is impregnated with X to help form the pellet and maintain shape, and also to aide combustion. The pellets are generally small and cylindrical in shape, about the size of a AAA battery. The boiler has storage towards the rear of the unit which then allows pellets to drop into the combustion chamber to be burned,  an automatic sensor allows more pellets to be dropped into the chamber as needed. There are systems which have a large hopper which can hold several day’s worth of pellets, which then feeds directly into the boiler storage.

The burning of wood only releases Co2 into the atmosphere that would have only been released as the wood decomposed, so in essence is carbon neutral.

Benefits
Using compressed saw dust pellets is a natural and sustainable method of providing space heating and hot water, thus reducing the demand on gas and saving many tonnes of Co2 a year. With pellets coming from managed forests and timber merchants it completes a cycle and uses what would have been a waste by product.

Downside
Wood chip boilers can use up to several tonnes of pellets a year, when ordering pellets they come in half tonne pallets which requires a dry storage space, this can be an issue for some properties. With a self feeding system the noise of the hopper feeding the storage area can be an issue for some people. There have been problems of incorrect set up and the boiler using more pellets than specified, as always having a system installed by qualified personnel is very important.

Types
Although there are many models around they can be broken down into 2 types manual feed and automatic. One has a small storage area, which can hold about a day’s worth of pellets and needs human intervention to top up. The other has a hopper located away from the boiler – can be through a wall for example, and can hold several day’s worth of fuel.

Considerations
• Size of the unit depending upon demand
• Space available for unit and hopper if automatic feed
• Space available for storage of pellets
• Cost of installation
• Maintenance cost – like a gas boiler requires service once a year
• Planning permission if installing a new flue

Cost
Units can vary from £5,000 - £12,000.

Sustainability
Wood chip boilers if installed correctly and burning as they should, could potentially save you some money that you would otherwise spend on natural gas, this again is dependent upon other factors, namely the energy efficiency of the property to reduce the overall need for space heating. At the worst case you would not save any money on your heating bill, but you would reduce the demand on natural resources and Co2 emissions. The main bulk of the units are metal, so limited embodied Co2, with some unit manufactures being in the UK. There are also pellet manufacturers and suppliers in the UK also . back_to_top

Biomass Boilers

How it works
Biomass boilers and stoves, can use a selection of fuels to burn; from seasoned timber, pellets and various smokeless fuels, to provide space heating and hot water, or just space heating. The burning of wood only releases Co2 into the atmosphere that would have only been released as the wood decomposed, so in essence is carbon neutral.

Benefits
Using timber is a natural and sustainable method of providing space heating and hot water, thus reducing the demand on gas and saving many tonnes of Co2 a year. With timber coming from managed forests or from local suppliers it is a perfect fuel, helping in some areas local business.

Downside
Storage of wood could be an issue, as would be finding a supplier if in a city, but not majorly. The main consideration with biomass boilers especially a new installation is the flue and the fitting of, plus the Planning department with the Clean Air Act. (need to check)

Types
There are a vast majority of models, sizes and styles. Some more efficient than others, there are a couple of models which have a secondary burn, this reuses the exhaust gases a second time round to burn off any excess carbon. The effect is a more efficient boiler or stove.
 
Considerations
• Size of the unit depending upon demand
• Space available for storage of wood
• Cost of installation
• Maintenance cost – like a gas boiler requires service once a year

Cost
Units can vary from £5,000 - £12,000.

Sustainability
As the wood burned only releases Co2 that would have been released once the tree had decomposed, the effect is carbon neutral. As long as the wood comes from properly managed forests, it saves gas and electricity dependency. The savings in Co2 are several tonnes a year . The main materials used are cast iron or steel which has a fairly low embodied Co2. back_to_top
 
Photovoltaics

 

How it works
Like solar thermal, photovoltaic’s (PV) harness the sun’s energy to create electrical power instead of hot water. PV since the late 1960’s has been transformed from its niche space travel origins, to today being one of the biggest areas for growth in green technology with every major player be it Sharp ,Shell, GE or BP all having research programs to develop new and more energy efficient cells. Many of the companies involved in manufacturing integrated circuit boards, flat panels and disk drives are using their expertise in semi conductors to propel the growth of PV cells.  At the moment PV cells are only about 15-18 % efficient, so in some ways it’s like the design of the early combustion engine and will only evolve into something quite spectacular.

As a green or sustainable energy, PV is regarded as one of the cheapest micro generating systems as solar energy is free to all. PV works by absorbing the photons from the sun’s rays using semiconductors to transfer electrons to create a flow of energy. Various types of materials are used in the manufacturing processes creating a hard crystalline cell or a thin film cell.

Like solar thermal, PV is generally mounted on a roof, but can be mounted on flat or vertical surfaces and even on a pole. One important factor to be aware of is that any overshadowing of the module will reduce the effectiveness due to the cells that make up the array are all linked, and reliant upon its neighbour. PV cells create DC current which needs to be converted into AC for use in the home (unless using a battery bank), an inverter does this and is normally sited near to a modern fuse box with circuit breakers.

Benefits
Solar energy doe not cost anything. The energy generated by PV can vary considerably, but a standard sized array is approx 1.5kwp for an 8m2. This could produce about 25% of your energy needs. During the summer months when your energy demand is lower, know that, while the suns shinning your exporting the power and getting paid. PV is extremely very low maintenance, no moving parts.

A PV system mounted to a roof with the inverter before the main fuse board.

Downside
The initial cost of PV is higher than say solar thermal. Partial shading will drastically reduce the efficiency of the array, as will overheating to a lesser extent. The other potentail for a reduction in efficiency especially in cities is the build up of urban grime, and simply needs cleaning, but if left unchecked can have a severe effect on performance. If the feed in tariffs are disappointing low, minimising financial gain to be had by exporting energy. Cells can be susceptible to both electrical and mechanical damage. The cost of manufacturing PV cells has drastically reduced over the last 10years but still not reached a point where sales and production costs have been reduced to challenge that of coal or gas as a viable alternative to mass scale power generation.

Types
The type of semiconductor used varies depending upon the manufacturer; silicon, crystalline silicon and cadmium telluride to produce different cells such as polycrystalline, monocrystalline and thin-film. Each type has a different approach to the same problem of; converting photons into usable energy, manufacturing costs and unit efficiency. 

Considerations
• Any roof/s that are south facing?
• Is the roof area shaded? or partially shaded?
• The pitch of the roof nominally 20—50 degrees.
• Structural integrity of the roof – will the roof take the imposed load of the unit?
• What is the demand for electricity – how many people live in the house?
• Type of fuse box present – will need to be a modern circuit breaker type.
• Cost of the installation
• Will Planning approval be required?
• Maintenance of the system – will a scaffold be required every 2 -3 years to gain access to the roof.
 
Costing
A standard unit for a small family is approx £8,000 - £12,000.

Sustainability
Silicon is the most abundant material on the planet, with others not so, it is the manufacturing process which requires considerable energy. Although some Chinese companies recon they can produce cells for $3/m, again this brings into question the inherent Co2 costs of transportation. On the whole, given the total financial and environmental costs, PV is a viable solution and could save about 1 tonne of Co2 from a standard size unit. back_to_top
 
Wind Turbines

How it works
Man has been harnessing the power of the wind for centuries, and in the 21st century it is no different. From onshore and offshore wind farms to the latest architectural designs where the flow of wind around and through a buildings structure is being used with wind turbines for power generation, a very clever use of innovation and design.

Wind turbines use the wind to turn blade or foils; this is then used to turn a motor through a gear box to generate electrical power. In smaller sized units for domestic use, the output is a DC current and requires an inverter to AC for use in the home or export to the National Grid. Domestic models can be mounted; directly onto a roof, attached to a gable end wall using a pole, through the roof onto the main structural supports or located in the garden or field if available.

Benefits
The potential to generate electrical energy is quite considerable, especially when 40% of all the wind that is blown across Europe is blown across the UK. With feed in tariffs in 2010 we can generate energy and get paid for it.

Downside
At present there is a lot of confusion regarding wind turbines and the data associated with manufacturers claims of power generated for given wind speeds. There have also been several small scale tests with domestic wind turbines and the results from these appear to be debilitating for wind technology on the domestic market, although these tests themselves have provided much debate as to their efficacy.

The main issues with wind turbines are 4 fold;
• Correct data from manufacturers regarding power to wind speed figures or curves
• Location of the property and its suitability for a wind turbine
• Correct mounting of the wind turbine
• Choosing the appropriate type of wind turbine

There is insufficient data on turbines which are mounted onto the structural frame of the roof or building, and the effects of vibration on the structure. With horizontal turbines the noise of the turbine as it spins creates an odd humming or drone, which some might find distracting or annoying.

Feed in tariffs being lower than expected and minimising earning potential

Types
Horizontal: This is the one that everyone knows and recognises. It has 3 blades that are attached at 120 degrees to each other, looking rather like petals on a flower, they are mounted onto a motor which sits up in the air and when it turns it rotates in the horizontal axis.

There are several limitations and maintenance issues. The turbine requires a minimum wind speed to begin to generate energy, like wise there is also a maximum wind speed at which the turbine can safely operate.  The turbine needs to be facing in the right direction to capture the wind, and is inflexible to changes in wind direction.

Then there is the issue of vibration as the blades are mounted horizontally this requires a perfect balancing act, not only the alignment of the blades in relation to each other but also the individual weight of each blade. Any slight damage or error in installation will result in excess vibration. Lastly there is the issue of maintenance; the motor sits atop a pole, this limits access to service and repair and might require high access equipment.

 Vertical Axis Wind Turbine (VAWT): Where the horizontal system looks like a flower, the vertical turbine can look like a giant egg whisk, a large drill bit or a stick man with arms out stretched. The design of the foil or blades might vary but the concept is the same.

Having the gearbox and motor mounted at the base, it benefits from any maintenance or service requirements as being close to the ground does not require high access equipment. Due to the foil or blades being mounted vertically they are more adaptable to site positioning and changes in wind direction. The vertical turbine can operate at lower speeds and with significantly less vibration. Like the horizontal turbine the system will have a minimum generating wind speed and maximum wind speed the turbine can safely operate.

There are limitations of the vertical design, as the blades spin they collect power from the wind in 2 opposite directions this creates a pulse and at a certain speed this creates a natural frequency that wants to cause the blades to vibrate and fail. VAWT also need to be a minimum distance from the ground so that the bottom of the foil or blade is able to capture any wind.

As the unit rotates it creates immense torque and the forces exerted upon the structure are huge. As the whole unit spins it creates centrifugal force, flexing the foils as the unit is being compressed as the centre of the foil wants to elongate. This requires the structure to be securely mounted with additional guide wires to anchor the turbine (depending upon size). Due to the forces involved the foils are manufactured using specialist materials, which can increase manufacturing costs.

VAWT are generally regarded as non self starting.

Considerations
• Average wind speed in the local area
• Positioning of the wind turbine
• The structural integrity of the roof if to be mounted there on
• Choosing the correct type of turbine
• Energy requirements if planning to live off grid
• Type of fuse box – a modern circuit breaker type will be required
• Cost of the system
• Planning approval will be required
• Maintenance issues and associated costs

Cost
This can vary from £8,500 up to £20,000

Sustainability
Using composite fibres and polymers to manufacture the blades, these are synthetic and require petro chemical products. The resins used are toxic to man and the environment. Wind turbines have like all systems carry a substantial amount of embodied Co2 in their manufacture, not to forget transportation costs.  Then there is the environmental impact to the wild life and to the owners or residents, in general this environmental impact is very low, it would be interesting to compare the number of dead animals/birds from wind turbines compared to our 10 million cars in the UK alone! Given the overall life of the system and the potential for living off grid and small scale generation, this far outweighs the negative environmental impact. back_to_top