Renewable Energy and the rest...



The different sources of energy are:




Heat Pumps


Heat pumps can be ground or air source.  The general principle of the heat pump operation is the same for each type.  It is the method of initially extracting the heat which differs.
Ground source heat pumps work by installing a loop below ground.  The upper six metres of ground remains a constant temperature of 10-16c throughout the year.  Water and anti freeze is circulated around the loop, which is fed to a heat exchanger. 
Air source heat pumps are similar to a fridge in reverse.  They work by extracting heat from the air when the external temperature is as low as -15 degrees centigrade.  A fluid is pumped around the system at a lower temperature than the outside air.  During the pumping it absorbs the relative warmth of the outside air and increases in temperature. 
Whether the fluid has extracted heat from the ground or the air, the fluid is passed through a heat exchanger.  The resulting low grade heat is subsequently passed through a compressor in the heat pump, and the concentration process heats up the low grade heat for heating purposes. 
The resulting heat can either be used 'air to air' e.g. to heat up the air directly, or 'air to water'.  The heat output from a heat pump is at a lower temperature than gas boilers - they are most effective when used with under floor heating, and the home is well insulated.
Typical costs for a ground source heat pump are in the region of 9,000-17,000, giving annual savings compared to electricity of 610.  The payback period is up to 28 years, with annual carbon savings of 5,270kg*.
Typical costs for an air source heat pump are in the region of 6,000-10,000, giving annual savings compared to electricity of 610.  The payback period is up to 16 years, with annual carbon savings of 5,270kg*.
Considerable savings in both costs and payback periods may be obtainable through the Government's Renewable Heat Incentive and Renewable Heat Premium Payment scheme.        



'Biomass' refers to a boiler using sustainable fuels - the most typical is a biomass boiler using wood chippings.  The chippings themselves comprise wooden pellets, which are sustainable when bought from certain suppliers who source their wood from purpose grown forests which are replanted.
Wood chippings can reduce your carbon emissions if the trees which provided the chippings are replanted.  This is because the carbon emitted while burning in your home is the same as that absorbed over the years as the forest was growing.  Carbon emissions are reduced to a bare minimum if the pellets are sourced from local suppliers.
You can install a 'standalone' to heat one room (although they can sometimes be provided with a back boiler to heat hot water), or connected to a central heating system and domestic hot water supply.
Seek help with the location of the boiler, the suitability of the flue, whether you are located in a smokeless zone, and whether the boiler can be installed safely.   
Typical costs for a pellet stove are in the region of 4,300, giving annual savings compared to electricity of 580.  The payback period is up to 8 years, with annual carbon savings of 7.5 tonnes*.    


Solar Photovoltaic Electricity Panels 


These panels capture the sun's energy using photovoltaic cells, and convert it into electricity.  Optimum performance is on a sunny day, but they can also operate on cloudy days.


The panels are made of silicon.  When the sun shines on a cell, an electric field is created across the layers.


An average system can generate 75% of your electricity needs.  In addition, the Government's Feed-In Tariff can generate just over 1,000 p.a.  This amount is paid irrespective of whether you use the electricity or export it to the grid.   


Typical costs for a 2.9kWp system are in the region of 11,700, giving annual savings of 1,200.  The payback period is up to 10 years, with annual carbon savings of 1 tonne*.    


Wind Turbines


Wind turbines use the wind to generate electricity.  Our view is that most benefit would be obtained from an exposed site, where more than enough electricity would be generated to power lights and electrical appliances.  


Turbines can either be pole mounted, or mounted on a building.  


Wind turbines are eligible for the Government's Feed-In Tariff.


Installation of a small roof mounted 1kW system costs circa 2,000.  Most benefit is obtained from installing a well sited 6kW pole mounted system, which costs in the region of 22,500, giving annual savings (if eligible for Feed-In Tariffs) of 3,200.  The payback period is up to 7 years, with annual carbon savings of 5.2 tonnes*.    




If you are fortunate to live near a flowing watercourse with sufficient head and flow, you may be able to benefit from hydroelectricity.   


Hydroelectricity works by the weight of water as it flows down a hill.  The water can turn a turbine, which in turns drives a generator to create electricity. 


Hydroelectricity is eligible for the Government's Feed-In Tariff.


Typical costs for a 5kW scheme are in the region of 25,000*.  Payback and carbon savings depend on the number of hours that the unit is able to run in the year - flow rates would need to be ascertained prior to installation.  


Micro Combined Heat and Power


Micro-CHP works by generating heat and electricity simultaneously, with electricity being generated as a by product. 


Various systems of this new technology are coming onto the domestic market.


Micro-CHP is eligible for the Government's Feed-In Tariff.


Costs, payback and carbon savings depend on the type of unit to be installed.


Mechanical Heat Recovery Ventilation


Not strictly renewable energy, but it could reuse existing heat in your home. 


When you shower in the morning, or cook in the evening you will create warm, moist air.  You will most likely mechanically extract this air, open the window or either of these combined with trickle vents to remove it.   
There is a way that you can recover the heat (and energy) from this warm air to help warm your home in the winter months.  In addition, you can remove stale air from other rooms and benefit from a constant supply of fresh, filtered air.  
You can achieve the above by installing a heat recovery system.  It uses ductwork suspended above ceilings to extract warm, moist air from bathrooms and kitchens.  This 'stale' air is used to warm incoming fresh air, which is ducted to all other habitable rooms.  These two types of air do not actually mix, but they are passed over a heat exchanger.  This recovers the heat and energy which would otherwise be lost. 


Some heat exchangers can be up to 90% efficient.  Their filters are very powerful and most eliminate the causes of asthma. 
Typical costs are in the region of 4,000-6,000.  Annual savings in costs, carbon and payback period depend on the extent of air tightness in your home.   
And the rest....
Condensing Gas Boilers
If the particular circumstances of your home do not permit more efficient, renewable sources of heating, you should at least convert from a traditional to a condensing gas boiler.
Very old gas boilers were typically only 55-65% efficient.  Current non condensing boilers have an efficiency of circa 78%.  Modern condensing boilers have an efficiency of 84-92%.   
A condensing boiler will reduce your gas bill by using the warm exhaust gases to heat the incoming air which goes into the boiler.
A condensing boiler can be used to 'feed in' extra warmth in extreme conditions to some of the alternative methods of heating described in this section.   
Typical costs are in the region of 2,300, giving annual savings of 300.  The payback period is up to 8 years, with annual carbon savings of 1,220kg*.
If you would like to view the blog on the green conversion and renovation of a Victorian London apartment, click here.


*Energy Saving Trust 2011.  2007 Privacy Policy Terms of Use