Green Energy > CHP
Micro CHP is an emerging technology with great potential
Combined heat and power (CHP) integrates the production of usable heat and power in one single, efficient process.
CHP generates electricity whilst also capturing usable heat that is produced in this process. This contrasts with conventional ways of generating electricity where considerable heat is simply wasted. In today’s coal and gas fired power stations, up to two thirds of the overall energy consumed is lost in this way, often seen as a cloud of steam rising from cooling towers.
To portray CHP in its simplest form consider a car. A car engine effectively becomes a CHP plant as the heat from the engine is used to heat the interior of the vehicle.
CHP is most efficient when heat can be used on-site or very close to it. Overall efficiency is reduced when the heat must be transported over longer distances. This requires heavily insulated pipes, which are expensive and inefficient; whereas electricity can be transmitted along a comparatively simple wire, and over much longer distances for the same energy loss. Today, sophisticated CHP plants can reach in excess of 80% efficiency at the point of use.
Although CHP has predominantly been used in industrial and commercial operations it is becoming more popular in the domestic market as home owners are becoming more aware of fuel costs and fuel security issues. This is commonly referred to as Micro-CHP and the operating principles remain the same.
Domestic micro-CHP systems are currently powered by mains gas or LPG; in the future there may be models powered by oil or bio-liquids. Although gas and LPG are fossil fuels rather than renewable energy sources, the technology is still considered to be a ‘low carbon technology’ because it can be more efficient than just burning a fossil fuel for heat and getting electricity from the national grid.
Micro-CHP systems are similar in size and shape to ordinary, domestic boilers and like them can be wall hung or floor standing. The only difference to a standard boiler is that they are able to generate electricity while they are heating water.
The hours of electricity production will not always match the hours of electricity consumption so a grid connection is always necessary. This can be used to buy electricity when needed but can also be used to sell excess electricity to the grid.
CHP is typically used in large scale industrial applications such as hotels, hospitals, industrial and commercial buildings where a constant source of heat and power is needed. At Local Government you will commonly see it used in leisure centres. However, this technology is currently being tried and tested in the domestic market.
There are several benefits to CHP both financial and environmental. The financial benefits include energy savings as electricity generated is at a lower cost than that provided by the grid; and the repayment of excise duty on fuel bought to power the plant which is underpinned by law and supporting regulations.
As CHP systems require less fuel than equivalent separate heat and power systems to produce the same amount of energy, environmental benefits are achieved through the reduction of carbon dioxide giving a reduced carbon footprint. For every unit of energy (heat or electricity) produced by a CHP plant from its input fuel, the levels of Carbon dioxide, oxides of nitrogen and sulphur dioxide emitted are less than half of those associated with a conventional coal-fired power station.
Another important benefit from operating a CHP plant is that it provides a degree of fuel security and can make energy go further through more efficient use of fuel. CHP plants also give the operator more flexibility in terms of energy and electricity choice. An increased number of CHP plants can reduce the demand from centralized power stations therefore reducing stress on the electricity power grid.