Clean electricity production must increase massively to replace fossil fuel combustion
In the fossil fuel-free energy scenario for Finland, the share of electricity will increase by about 50% replacing fossil fuels. More electricity will be needed to supply power for the heat pumps in district heating networks and buildings, and electric vehicles in the transport sector. Also steel industry and other industries need clean electricity in order to replace fossil fuels in the heating and the industrial processes.
The increasing electricity will be supplied largely by wind power, which will represent half of the annual electricity production in the 100% fossil-free scenario. In other words, the amount of wind power production will then be ten times as high as in 2017. Solar power production is assumed to be about 5% of the wind power production but its role will be to even out the daily variation of electricity demand. It also matches well with space cooling, which may strongly increase.
Figure 1. Electricity production in 2017 and in the 100% fossil-free scenario. The electricity consumption is assumed to increase from 85 TWh in 2017 to 125 TWh/year because electricity use will replace fossil fuel combustion in heating, transport and industry.
Power balancing in the energy system with high shares of variable wind and solar power
A high share of wind power causes high production peaks, as the nearly constant nuclear power production pattern remains with the new Olkiluoto 3 nuclear power plant. However, these peaks in power production can be utilized in many ways. For example, by converting electricity into heat for the district heating networks or increasing industrial processes with demand response automation. Also various technologies for the conversion of power to fuels are developing.
Figure 2. Estimated hourly electricity production in Finland during one year, with a 60 TWh capacity of wind power. Hydropower, combined heat and power (CHP) production in district heating networks and electricity imports are used to even out the power fluctuations. In practice, the CHP production curve is smoother than in the picture, due to the e.g. flexible power consumption.
In the scenario, an hour by hour balance for both heat and electricity demands is sought for. It is assumed that the hourly industrial CHP production remains as it was in 2017. The production timing of hydropower has a new shape to fit into the variable production of wind power. District heating CHP will also depend on the wind energy production pattern, aiming at filling the occasional gaps in the electricity production.
Bio-CHP plants can operate as backup power supported by other flexibility solutions; demand response automation, a flexibility of the heat pumps and storages enable several hours of time for the bio-CHP plants to adapt to the fluctuating wind power production and the power needs of heat pumps. In the scenario, the peak load time of the bio-CHP plants is approximately 3500 hours annually. Total running hours are more since the plants run also in partial power. This way, it should be feasible to upgrade existing CHP plants with fluidized bed boilers for 100% bioenergy. CHP plants with condensing tails or auxiliary coolers can also provide separate power production when there is no need for the heat, but electricity is needed and it cannot be imported. This kind of utilization of bio-CHP plants is less expensive than separate condensing power plants.
FAQ: “How to secure sufficient heat and electricity supply during very cold winter days, when the wind is not blowing?”
The low wind periods hardly ever last more than few days. At worst it can be one week, which happens extremely rarely. Therefore in the 100% fossil-free scenario the needed heat storage capacity covers approximately one week of heat demand.
During the cold days’ peak demand, the electricity prices are high if the wind is low at the same time. Figure below shows how the electricity system works when there is a lack or excess of electricity production.
Figure 3. During the coldest days of the year different energy sources, energy storages, demand response solutions, and imports and exports of electricity help to balance the electricity production and demand curves. The amount of imports in the 100% fossil fuel-free scenario is however low, only about a third of the 2017 year’s levels.
In the district heating networks, heat storages are discharged, when wind energy supply is low. This helps the heat pumps to run with high efficiency and low electricity consumption. District bio-CHP is used actively as back up power and heat.
In case of a threat of power shortage, mainly existing gas turbines or engines are used. The fuels used are currently fossil oil or gas, but in the future clean fuels can be used. The annual energy consumed by the gas turbines and motors is not high, currently and also presumably in the future, less than 0,1 TWh/year. This kind of capacity is and will be however needed. For example, the capacity in Fingrid’s reserve power plants is currently over 1200 MW.
Samuli Rinne, Karoliina Auvinen, Francesco Reda, Salvatore Ruggiero and Armi Temmes. 2018. Discussion paper: Clean district heating – how can it work? (pdf). Publication of the Smart Energy Transition project funded by the Academy of Finland’s Strategic Research Council.
Web articles: Finnish energy system can be made 100% fossil free and Clean district heating and cooling system – how can it work?
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