To CHP or not to CHP: That’s the question

Panel: 3. Policy, finance and governance

Author:
Erwin Cornelis, (Privé), Belgium

Abstract

Belgium is phasing out all its nuclear power capacity (5.9 GW) by 2026. This nuclear capacity will partly be replaced by new thermal generation capacity; a Capacity Remuneration Mechanism provides room for 2.3 GW of such capacity. Project developers are now submitting permit applications for projects, typically large capacity (800 à 900 MW) Combined Cycle Gas Turbines with a high electric efficiency (up to 63%) and no focus on excess heat exchange, which could lead to substantial conversion losses.

This contribution discusses the extent to which excess these conversion losses can be reduced by exploiting the excess heat potential for heating purposes.

First, it assesses the need for thermal power generation. Detailed simulation of the Belgian electricity system indicate a continuous need for thermal power generation, even in a scenario with a high penetration of intermittent renewable energy sources. In 2045, still 3.6 GW of thermal power generation might be needed, which is about half of the current 7.8 GW. According to the simulation, their load can be rather low: 2500-2700 hours per year.

However, a validation of the simulation results to the climatic conditions of a particular year (2016) indicate that the potential to exchange power with the neighbouring countries and the potential to store electricity might be overestimated. As a consequence, the need for thermal power generation might be higher than indicated in the simulations.

Second, it compares the potential of excess heat of the thermal power generation with the heat demand in the building sector; the remaining heat demand after renovating the buildings is still large enough to absorb this potential. Yet, this heat demand could – in theory – also be covered by other renewable heat sources.

Third, when tapping this potential of excess heat of thermal power generation, a decarbonised substitute for natural gas is needed. Biogas is one substitute, but its potential is low and it is already largely tapped at present. Green hydrogen is another substitute, but its production entails conversion losses that exceed the potential of excess heat.

Fourth, the excess heat potential of some of the currently planned power plants is assessed. This assessment reveals that district heating grids need to be deployed in a large area in order to tap the full excess heat potential. As this is less likely to happen, a multiple of smaller capacity power plants, spread of the country, might better facilitate the exploitation of the excess heat potential than a handful of large capacity power plants.

The conclusion of this contribution is that Belgium, as an areas with a low potential of hydro-power, depends to a substantial extent on thermal power generation for preserving the balance on the electricity grid, also on the long term. To decarbonise this energy production requires zero-carbon fuels. Yet, as the related conversion losses exceed the excess heat potential; heat integration should start from the production of these zero-carbon fuels. The exploitation of the excess heat potential can add to this, but the scale and the sites of the thermal power plants should be carefully selected to maximise this potential.

Watch presentation