Advantages of power generation with Combined Heat Power (CHP)

Power generation in CHP shows significant higher efficiencies than any other fossil fuelled power plant available today. Especially with natural gas this leads to lowest specific emissions of CO2. The specific investment per reduced ton of CO2 is low.

Therefore CHP is an important and powerful instrument for climate protection. To use most of its potential of reducing or limiting emissions in many locations a big part of the generated power has to be fed into the electric grid. This is due to thermodynamical reasons.

Estimations of potentials show that some 10 % to about half of the total power generation could be done in CHP. In countries with middle European climate most of this potential is located in industrial applications rather than in district heating systems. A good example with a high installation rate are the Netherlands. But Germany with a far lower actual CHP share should be able to achieve in the range of half of at least the fossil power generation in CHP. In the present park of German power plants this would result in a CO2 reduction of a third in power generation and about 13 % of total German green house gas emissions.

CHP offers good advantages for communal and especially industrial consumers of heat: energy costs can be reduced considerably more by CHP than by lower prices for power due to liberalised markets. Contractors specialised on planning, construction and operating CHP power plants share the economical benefits by lowering the heat prices for the customer.

The CHP topping cycle is a proven measure to validate the advantages of CHP: it defines the additional fuel of CHP for power generation and allows a easy calculation of its electric efficiency, which is much higher than that of the underlying power process without cogeneration. This focus on electricity generation allows a correct and direct comparison with other power plants. It is independent from the part of heat which is supplied by CHP in a local situation.

For medium sized industrial applications the efficiency of the topping cycle ranges from about

It has to be emphasised that these high values of the topping cycles are real electrical efficiencies: They can directly be compared to other power plants. They are different from the often used overall efficiencies including power and heat. The electric efficiencies of CHP topping cycles are in any case far above those of any other fossil fired power plant. So they result in equivalent low specific CO2 emissions.

Integrated into a strategy for lowest overall emissions it is import to look at the corresponding values of the power to heat ratio: for the combined gas and steam turbine cycle without supplementary firing it is about 4 times as high as for poor steam turbine cycles. The capability of the energy to produce power - or in thermodynamical terms the Exergy - is best used in this cycle. So it is the preferable one to produce power with lowest emissions.

Then in many cases a lot of power has to be fed back into the grid. Condition for realisation is economical validity: The earnings by selling CHP power must be high enough to pay for the additional investment and operating costs of CHP.

In liberalised markets and markets changing into liberalisation this power competes directly with generation in old depreciated power plants and biggest new combined cycles (but not cogeneration). So only biggest CHP (in the range of 100 MW and more) is really competitive. Actually many industrial applications with a heat demand of some 10 MW to far over 100 MW are operated either in partial CHP to serve the local power demand only or are even turned back from cogeneration to the separate generation of heat and power with much higher overall emissions! All this happens though Least Cost Planning (LCP) will show CHP as most attractive instrument to lower emissions.

To use the big potentials of CHP liberalisation has to be re-regulated partly. This is explicitly favoured by European Electricity Directive. It must and can be done avoiding discrimination of industry and wind fall profits. It is necessary as well for the markets in central Europe as well for the eastern countries being actually in a much faster transition process. It is hard to change a new infrastructure which has just developed under wrong framework conditions. Self commitments of industry to lower their emissions are supported.

The benefits: Developing highly sustainable energy structures including an adequate portion of cogeneration, lowers greenhouse gas emissions significantly, initiates investments and thus increases employment, international competitiveness and thereby social and economical stability.

Fuel cells of different size and type commercially available in the next decade will offer big new advantages for cogeneration. They need an adequate economical framework as well.