Tuesday 18th of June 2019, Poul Alberg Østergaard, Professor at the Department of Planning at Aalborg University, gave a webinar on ‘Electricity storage in the Danish energy system’.
Poul’s research is focused on how different sectors can work together in a future energy system highly based on renewables. Denmark already has a lot of wind energy in the Danish electricity grid, and the time where the wind production is bigger than the consumption has become higher and higher the last couple of years and will continue to increase in the future. Denmark is moving away from easily storable fuels to an integrated energy system, where different sectors have to work together, e.g. electricity, heat, and transportation. As it is today, can we import or export electricity from our neighbor countries, but as they also will have more fluctuating wind and solar energy in their system, we have to manage the energy balance nation by nation. A lot of the balancing can be done by controlling the consumption intelligently, e.g. charging electric cars when there is a surplus of wind and turn off heat pumps when there is a lack of wind. However, it will still be necessary to store electricity. Unfortunately, it is very expensive to store electric energy in comparison to other types, e.g. oil, coal, hot water, etc. Poul, therefore, mentioned, that it might be cheaper to oversize for example PV (photovoltaic) systems than buying storage capacity.
Electric energy can be stored in different ways. Poul mentioned Compressed Air Energy Storage (CAES), pumped hydro storage and batteries. CAES and pumped hydro storage are much cheaper than battery storage and are capable of storing a huge amount of energy. Both of them, however, requires geographical conditions to be feasible. Obviously, Denmark isn’t suitable for pumped hydro storage due to the lack of mountains. Even though we have salt domes (used for storing natural gas) we still need additional battery storage. Poul pointed out, that battery storage is expensive and that we almost get the needed electrochemical storage capacity for free in electric vehicles, as the battery in electric vehicles has been purchased for another purpose, i.e. personal transportation. According to Poul the need for storage of electric energy will be fulfilled largely by electric vehicles.
Several house owners have PV panels installed on their roof and some of them have even bought battery storage to increase the self-consumption. This works very well in the summer period, but unfortunately, they are strongly dependent on the electricity grid in the winter period. Poul and his team also made a study as to where the battery storage would be optimally located, he concludes that placing larger batteries communally on the grid is preferable to many small batteries on a household level. If the batteries are placed communally the power flow of the battery was following the wind production whereas on a household level the PV production profile determined the power flow.
You can see the presentation of Poul here: https://drive.google.com/open?id=1QpAJwvmfnSSzHjehWyL-phD7xX6yBWnZ