Microgeneration

Many renewable energy technologies can be implemented on widely differing scales – wind turbines, for example, can range from a tiny unit installed on the roof of a private house (Malcolm Wicks, the UK Science Minister, has one installed on his own house) to huge offshore wind farms involving hundreds of giant turbines. Solar PV can likewise range in application from small panels on the roofs of private houses to huge installations covering areas the size of many football pitches. It is likely that as renewable energy systems develop there will be a mix of large-scale and small-scale installations with different countries placing a different emphasis on the balance between the two.

Some innovative initiatives are currently resulting in ‘eco-houses’ that are able to function as ‘mini power plants’ with combinations of roof-top solar PV units, small wind turbines and heat pumps, providing not only all of the heat and power required by the individual house but also having enough left over to sell back to the grid at certain times or to provide the electrical power to, for example, charge a small electric vehicle.

Microgeneration is a term that is now being used for the generation of low carbon heat and power by individuals, small businesses and communities, largely to meet their own needs. Technologies for use in microgeneration applications are improving rapidly both in terms of cost and the practicality of installation and usage. Current options for microgeneration include:

• small-scale wind turbines, which can now are very affordable to install
• solar photovoltaic units that can be mounted on roof tops, and also solar roofing tiles which can actually be used directly as a roof covering
• solar hot water systems, which can also be mounted on roof tops, but directly provide hot (or warmed) water for use in heating, bathing and cooking
• micro combined heat and power (MicroCHP) installations use boilers burning biomass, gas or other fuels to generate both heat and electricity for a single household (this is far more efficient than using fuel just for heating or electricity)
• small-scale hydroelectric plants, which require a small stream or river with a significant drop in height (so only applicable in certain places)
• ground source heat pumps, which typically use an electrically driven heat pump to provide space and water heating, but use only one quarter of the electricity that would be required to provide heating directly.

In addition to the equipment for renewable energy generation, an energy storage device and equipment for power conversion are required in a microgeneration set-up. Although a hook-up to the regular electricity grid is not essential, it helps to decrease costs by allowing participation in schemes that allow users to sell electricity back to the grid.

Research commissioned by the UK government has suggested that a substantial portion of energy generation in the UK could eventually be supplied from microgeneration. Currently however few microgeneration technologies are directly cost competitive for electricity generation (as compared to large-scale coal power plants) but biomass heating and ground source heat pumps can already be highly cost effective when compared to electric heating systems. The trend in the coming years will likely be one of other microgeneration technologies becoming increasingly cost effective as market uptake increases and the technologies are improved. The research indicated that MicroCHP installations are closest to reaching cost competitiveness, followed by small wind power systems and then finally domestic PV systems. (Source British Council, report August 2008)