This article has been sourced from www.cogen.cz and provides an overview of the situation in the Czech Republic. Nevertheless, numerous arguments presented hold general validity.
1. Photovoltaics only serve as a supplementary solution for energy requirements.
Despite their easy installation, photovoltaic systems have a significant drawback in that their winter output is only about 20% compared to summer. This poses a challenge, particularly in countries with climates where the energy demand during winter is several times higher than in summer.
Attempting to maximize photovoltaic output often proves counterproductive. For instance, in companies, there is no practical way to utilize weekend production. As a result, photovoltaics typically covers approximately 10-20% of the energy demand.
The potential of other renewable energy sources such as biomass, biogas, and waste are limited. Additionally, the growth of wind energy is hindered by various factors, leading to slow progress. As a result, in many cases, there is a need to continue using gas as an energy source. However, the focus is on maximizing efficiency through cogeneration, where electricity and heat are produced simultaneously.
2. Cogeneration is effectively complemented by heat pumps
Heat pumps are a highly promising technology; however, their suitability is not universal as they require specific conditions. In the case of air source heat pumps, their performance significantly decreases during winter. A mix of different, complementary sources is common at the state level or in large heating plants. This will become increasingly common in the future even for smaller sources.
Heat pumps excel in generating heat when electricity is inexpensive, while cogeneration systems thrive during periods of energy scarcity and high prices. Cogeneration will also strengthen the distribution network for the expected massive expansion of domestic air source heat pumps, which will act as direct heaters during winter peaks.
3. District heating is essential for the decarbonisation of the heating sector
Germany has launched an ambitious district heating initiative with the goal of increasing the proportion of heat supplied by district heating systems from the current 15% to an impressive 45%. Meanwhile, the Czech Republic holds a significant advantage, with 35% of its consumers already connected to district heating. This represents a valuable asset that should not be overlooked.
Heat networks, like electricity networks, will change from a one-way flow from sources to consumers to intermediaries between a range of RES and waste heat, supplemented by controllable gas CHP to meet winter peaks in heat and electricity demand. Communities should therefore primarily be built around existing district heating systems to take full advantage of the potential they offer.
4. Even a modest cogeneration plant outperforms a state-of-the-art gas power plant in terms of efficiency
A small cogeneration plant with a capacity of 50 kW exhibits an electrical efficiency exceeding 30%, while larger units of several MW can approach 50%. These cogeneration sources, precisely due to their relatively small size and proximity to electricity and heat consumption, achieve an impressive overall efficiency of over 90% in cogeneration mode, significantly surpassing the 60% efficiency of a steam-gas power plant.
By further optimizing the operation of the cogeneration plant and effectively utilizing all waste heat and employing waste gas condensation through a heat pump, it becomes possible to achieve efficiencies surpassing 100%.
5. The potential for cogeneration is huge
Wind or batteries will not replace coal-fired sources in winter. In the summer, renewable energy sources (RES) will suffice for our energy needs. In winter, however, the situation is considerably different. The maximum load exceeds 12 GW and is set to rise due to expanding heat pump installations in district heating and industry. To achieve the 2033 coal phase-out, replacing 6 GW of coal-fired power stations with gas-fired sources for peak demand is necessary. When considering the potential of alternative heat sources such as waste, heat pumps, and biomass, predictions for heat consumption indicate the possibility of constructing up to 4 GW of cogeneration capacity. Abandoning gas by municipal and community heating systems would be undesirable, potentially requiring subsidies for less efficient combined cycle gas turbine (CCGT) plants during controllable resource shortages.
6. Cogeneration produces electricity and heat even in the event of a blackout
How long can you maintain your “independence and self-sufficiency” during winter using PV and batteries? The gas grid is independent of electricity and will be operational even in the event of a major blackout. Local CHP can keep critical infrastructure (important offices, wastewater treatment plants, etc.) running. Decentralised energy is in principle less vulnerable to attacks, both cyber and physical.
7. Cogeneration is not threatened by cannibalization
With just one year of intensive PV construction, we are already encountering limitations in the current system, evident in negative electricity prices. It is necessary to look for ways to use variable production – electrification of the heat sector (electric boilers, heat pumps), storage in batteries, in the future electrolyzers. This will enable the shutdown of coal-fired power plants during summer, as they are unable to cease operation for short periods and are willing to pay for the electricity they consume. However, these measures will lag behind the rapid pace of PV installations, and low prices during sunshine periods will become a permanent phenomenon. Even CEPS (The Czech Transmission Operator) has already warned that investors should expect 20 % less revenue as they will have to shut down due to grid congestion. In contrast, very fast-starting CHP can be operated in a controlled manner during times of peak electricity prices and also benefit from the growing demand for supporting services
8. The future lies in a combination of RES, nuclear and green gases
Differentiating between gas as a fuel and gas technology is crucial. While we have primarily used Russian gas in the past, we are gradually transitioning to gaseous or liquefied natural gas from other suppliers. Biomethane, to a limited extent, is one option, followed by a gradual shift towards hydrogen and other synthetic fuels derived from surplus renewable electricity or imported from countries with favourable conditions. Other gaseous fuels – biogas, mine and landfill gas – are used at the local level. Gas technologies, such as engines and combustion turbines for larger installations, are currently the only industrial-scale options for converting these green fuels back into electricity and maximizing energy efficiency through cogeneration.