08/11/2023
Source: Energy & Management Powernews
What role the efficiency technology combined heat and power takes in the current political discourse, has B.KWK President Claus-Heinrich Stahl in conversation with E&M classified.
Heat makes up about half of the annual final energy consumption in Germany. It is generated, however, only from 17 percent renewable energy, of which about 80 percent from biomass. In the building sector, it accounts for almost a third of CO2 emissions. This is set to change in the future. In order to make the heat supply greenhouse gas neutral, the traffic lights want to introduce two new laws: The Building Energy Act (Gebäudeenergiegesetz, GEG) and the Heat Planning Act (Wärmeplanungsgesetz, WPG) provide for a transformation of the heat supply with renewable energies. The WPG is to regulate that large cities must submit where they plan district heating networks by 2026, while smaller cities and municipalities have until 2028. Only then will the provisions of the GEG become relevant for building owners.
With the timing and content of the laws on each other, a requirement essential for the Federal Association of Combined Heat and Power (B.KWK) is implemented. "Clever heat planning and the use of efficient technologies can massively reduce CO2 emissions in the building sector," explains Claus-Heinrich Stahl, president of B.KWK. "In this respect, we as an association fundamentally welcome legal changes that advance the heat turnaround." In unison with one another WPG and GEG are to form in the future a stable foundation, in order to arrange the heat supply step by step greenhouse gas-neutral.
In the current draft to the GEG amendment the Kraft-Wärme-Kopplung is however neither explicitly designated nor sufficiently considered, by talking about condensing boilers for peak load production, criticizes the KWK federation sharply. "It is incomprehensible why CHP is not to play a role in the supply of buildings and building networks that fall within the scope of the GEG. It is, correctly used, by far more economical and also more pollution free than for example gas heatings, since KWK plants can be already operated today with biogas, wood gas as well as with admixture of EE gases to the natural gas", lead out steel. A corresponding recommendation paper of the B.KWK is present to the policy.
Residual load is too little considered
In particular in combination with heat storages, heat pumps and Photovoltaik the KWK represents also in the object and building net supply an efficient possibility of the simultaneous production of warmth and river for the reduction of greenhouse gas emissions. Especially in the heating periods from October to March, the power supply from photovoltaics is naturally limited. At the same time, air-to-water heat pumps record their most inefficient performance figures at very low temperatures. These are the hours and days of the year when residual load must be covered, i.e., the share of electricity demand that cannot be met by fluctuating renewable energies. Decentralized CHP plants represent an optimal solution here, both ecologically and economically, explains the B.KWK.
Because CHP combines electricity and heat generation in one and the same process, it avoids wasting energy and resources and makes the best possible use of the fuel used. CHP plants thus have an overall efficiency of up to 97 percent, according to Stahl, saving significant amounts of CO2. Conventional power plants, which dissipate heat that is generated unused and thus heat ambient air or water, achieve a maximum of 40 percent and pollute the environment many times over.
"Residual load is an aspect that has hardly been taken into account in the planning of the energy turnaround, although it is enormously important for the energy supply. Electricity demand will continue to rise, and with it the residual load. This will continue to require highly flexible power plant capacities on a significant scale," Stahl explains. "If you think of fluctuating wind and solar energy as the hull of a modern energy supply, cogeneration is its backbone, able to supply electricity and heat in a controllable, stabilizing manner at any time," Stahl continues. "It is needed just like the fire department when there is a fire."
From endurance runner to sprinter
The climate-neutral heat supply of the future will require many building blocks, according to the B.KWK. Electrification and efficiency as well as district and local heat supply and renewable gases. CHP is an important building block of the whole, it said. "The association of cogeneration with CO2-intensive fuels is still widespread. Yet CHP has long been on its way from being a gray perennial to a green sprinter," Stahl says. "The role of CHP must continue to transform in order to provide greater support for the renewable energy system in the future. Powered by sustainable gases and used selectively to cover residual load, CHP is an important tool for the energy transition."
He says CHP offers a number of advantages that can be used to decarbonize the heat supply. For example, modern CHP plants can already be operated with hydrogen admixtures - after a conversion or retrofit, one hundred percent hydrogen operation is also possible. In addition, according to the association, they can generate electricity and heat with domestic biogas or biomethane, or with wood gas, mine gas or sewage gas from local waste management. CO2-binding biochar can be produced in combination with wood gas CHP.
In addition to electricity, heat and cooling, it also converts woody residues and waste materials into plant charcoal, which can then be used as plant fertilizer, concrete additive in road construction or for activated charcoal filters to bind CO2. As iKWK systems, heat pumps, power-to-heat, geothermal energy, solar thermal energy, industrial waste heat and photovoltaics can be combined with CHP plants.
"The crucial thing is to make the energy transition open to all technologies and to exploit the potential of all energy sources. In this way, renewable heat and electricity can contribute to a climate-friendly energy supply," says Stahl. "Intelligently combining processes and sectors reduces energy consumption, conserves resources and is therefore a key concept in the energy transition. With a view to a secure energy supply, cogeneration is its most efficient instrument.
In this respect, there is an urgent need for a rethinking of the legal framework and funding conditions and for a political discourse in which cogeneration plays a prominent role,
he adds, saying with a view to the coming fall: "We are continuing to exchange views and will give the legislature our recommendations on the specific form of the bills before they are passed in the fall."
Author: Heidi Roider
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