Making the most of CHP
Exploiting the benefits of combined heat and power (CHP) technology continues to grow in importance. In 2000 almost 6% of the UK’s electricity was provided by 1560 CHP schemes. The chemical, oil, paper and printing, and food and tobacco industries account for about 75% of CHP electrical capacity
As part of the UK’s aim for buildings to be carbon neutral by 2016, the use and associated benefits of CHP technology has jumped up both the political and building agenda. It is a highly efficient way to use both fossil and renewable fuels and can therefore make a significant contribution to the UK’s sustainable energy goals, bringing environmental, economic, social and energy security benefits.
NewEnCo, the New Energy Company, was established to exploit the benefits of microturbine CHP technology in this country and is the sole UK distributor for the leading micro turbine, Turbec T100.
What is CHP?
CHP is the simultaneous generation of usable power and heat in a single process. In its simplest form, it employs a gas turbine, an engine or a steam turbine to drive an alternator and the resulting electricity can be used either wholly or partially on-site. The heat produced during power generation is recovered, usually in a heat recovery boiler and can be used to raise steam for a number of industrial processes, to provide hot water for space heating or, with appropriate equipment installed, cooling.
Not only does CHP enable the conversion of a high proportion of otherwise waste heat to usable heat, it is very efficient because power is generated close to where it is being used (this means electricity transmission losses are minimised). The predominant fuel used for CHP schemes is natural gas (62% in 2000). Other fuels include oil, coal and now the growing area of renewables such as municipal and industrial waste, sewage gases, biogases from anaerobic digestion, bio-diesel, gasification and wood.
CHP typically leads to a 25-35% reduction in primary energy use and associated cost saving and is therefore 80% efficient, compared to 58% in conventional systems. CHP also generates less harmful gases such as sulphur dioxide, nitrogen oxides and particulates and in addition CO2 emissions and associated climate change impacts are reduced, particularly where renewable fuels are used.
CHP in action
For a site to support a successful CHP installation, it should typically have a heat and power requirement of at least 4,500 hours per year, although in some cases it could be cost effective with fewer operating hours. However once these criteria have been met it can prove to be an excellent method of generating power as proved at Coronation Nursery near Harlow, Essex where the nursery was able to generate enough power to serve their on-site needs and export the excess to the National Grid.
The installation consisted of five Turbec T100 CHP microturbine units. The T100 represents a major breakthrough in CHP technology and is the solution for all forward-thinking UK greenhouse owners. The added benefit of this solution is that it has the potential for other applications and with increasing costs and reducing income facing many industries like horticulture, the microturbine presents the opportunity to make significant savings and, as in the case of Coronation Nursery, an additional source of income.
The CHP microturbine project, which has a total capital cost in the region of £600,000, was partly grant funded under the DEFRA Rural Enterprise Scheme and provided an opportunity for the nursery to generate power for both on-site use and to export to the grid. Hot water from the units is integrated into the sites heating and storage system and the exhaust gas is used for CO2 enrichment.
Changes in the way electricity is bought, transmitted and sold in the UK allows power produced in one location to be sold to an end-user in another location. This means power exported from the site can be sold to the very supermarkets where the produce from the greenhouse is sold, providing the ultimate in green branding.
The unit produces electricity and heat fuelled by natural gas, and achieves an overall efficiency of 80%. While there is a range of applications for the T100, based upon the use of the heat and power, there is the added benefit of carbon dioxide enrichment when used in greenhouses. Emissions from the units are so clean that the exhaust gases can be used directly in the greenhouse.
Operating at full output, the Turbec T100 unit produces 100kW of electricity, 170kW of heat and approximately 90kg of carbon dioxide per hour. Micro gas turbines offer many advantages over conventional reciprocating gas or diesel engines because with only one moving part, they are inherently more reliable and maintenance costs are much lower than for reciprocating engines. They are also quieter, smaller and cleaner.
The microturbine can also be configured to run as a standby power source during periods when there is failure in the mains power supply.
While the current market demand tends to be for large-scale CHP systems, there is a greater potential for small-scale CHP in the UK as a result of the substantial political support and legislative pressure for its use by Government and Planning Authorities. The Turbec T100 is already well proven with more than 200 units now operational throughout Europe. The lead T100 has now completed over 40,000 operating hours and the average unit availability across the UK fleet exceeded 93% in 2006 and 2007.
NewEnCo currently has 55 units in the UK and anticipates a further 15 installations in 2008 across a wide range of applications.