In the Netherlands anno 2021, energy is mainly used to heat buildings such as houses (with central heating on natural gas, especially in autumn and winter), for lighting and to run appliances (in the form of electricity), to power cars and other vehicles (mainly liquid motor fuels made from oil), and in industry to convert raw materials into products. The latter includes the electricity and heat required by energy-intensive industries to make steel, silicon carbide, aluminium and plastics.
Dutch energy supply
But then again … this energy has to come from somewhere. The Dutch energy supply, with natural gas and oil (from our own soil or imported) as a basis, still largely has a fossil origin. These fuels – possibly after conversion into petrol or kerosene – can be used directly for combustion in order to produce energy.
Gas-fired power plants are the main source of electricity. A modern gas-fired power plant works like a two-stage rocket with a gas turbine and a steam turbine. In the gas turbine, natural gas is ignited together with compressed air in a combustion chamber, where the hot combustion gases carbon dioxide and water vapour are released onto the blades of a turbine. These blades are mounted on a shaft which is connected to an electric generator that converts the rotating movement into electricity. But there is more, for the residual heat from the hot combustion gases is used to convert water into steam, and this steam makes the blades of a steam turbine rotate. The steam turbine also generates electricity, in the same way as the gas turbine. Because the efficiency of a gas-fired power station increases with higher (combustion) temperature and pressure, high-temperature-resistant (super)alloys and ceramic coatings are indispensable.
The Netherlands also uses coal-fired power stations that are co-fired with biomass, and nuclear energy. Renewable sources such as sun and wind account for only a few percent in absolute terms in 2021, but they are strongly on the rise.
Why an energy transition?
Actually, we have always obtained our energy from the sun, even in the past 200 years. After all, coal, oil and natural gas are nothing but ‘captured solar energy’ in plants that had millions of years to convert into something that we now call fossil fuels. Oil, natural gas and coal are part of the long carbon cycle. The tricky thing is that the carbon dioxide (CO2) captured by the plants on the long run has, in a relatively short time, entered the earth’s atmosphere as a greenhouse gas – with all the bad (future) consequences this entails. This indicates the need for a transition from fossil fuels to a sustainable energy supply.
The driving force behind this energy transition is the reduction of CO2 emissions. There are various efforts to achieve this – in addition to energy savings, better thermal insulation or more economical lighting, which means you won’t have to use the energy at all.
With a value of 1.4, coal has a higher C/H ratio than oil (C/H ~ 0.6) or natural gas (C/H ~ 0.25). Shifting from burning coal to burning natural gas reduces CO2 emissions per unit of energy generated, possibly with options to capture and store CO2 directly. Other options are to make more use of possibilities to emit CO2 from the short carbon cycle by burning biomass (wood).
In any case, electrification is a trend in society, with more use of renewable electricity generated by wind turbines and solar cells (PV), for example for electric-powered cars and bicycles. Solar cells have a higher yield in the summer months, and wind turbines perform better in the winter. To ensure electricity production when the solar cell is not working (at night) or when the wind turbine is not working (when there is not enough wind or during a heavy storm), you have to find alternative solutions. For example, in the form of good storage possibilities in batteries or in the form of the energy carrier hydrogen via electrolysers, to store surplus of electrical energy when the sun is shining abundantly and the wind is blowing. ‘Surplus’ is emphasised here because the conversion of water into hydrogen involves a considerable loss of energy.
Another possibility is to supplement fluctuating renewable energy generation with stable energy generation from nuclear power, or by quickly putting gas-fired power plants into operation. In the short term, with natural gas as the fuel, and – after completing the energy transition to non-fossil – perhaps with stored hydrogen.
Although electrification is expected to eventually take over much of the current energy demand, this will not be feasible in all cases. Consider the energy-intensive industries mentioned above, where there might be an ‘active’ role for hydrogen as a fuel or reducing medium – in addition to the generally ‘passive’ role of hydrogen as a means of energy storage.