While sustainable energy is good for the environment, it isn’t as easy to generate as (grey) power produced from coal or gas. And this creates problems, because electricity supply and demand must always be in balance. What happens to the clean energy if the wind picks up around midnight and everyone in Western Europe turns out the lights? At ECN, researchers are already considering this issue. “The nature of the high-voltage network is changing. It was a transmission system and in 2020 it will be an exchange system.”

The sustainable energy sources wind and sun have a disadvantage beside the advantages: they don’t produce power to order. Nature has its own rhythm, which only runs in parallel with our energy needs a small part of the time. For example, the sun shines brighter throughout the day when we are more active and go to work. But in the dark days before Christmas, this doesn’t help much.
The issue seems far off; there isn’t yet all that much ‘green’ power capacity in Europe. But it is an issue and it must be resolved, states Martin Scheepers of ECN Efficiency & Infrastructure resolutely. “Ireland has a relatively large amount of wind energy with respect to the total power capacity, and it has a limited link with neighbouring country England. This has already caused regular problems for the Irish, due to the inconstancy of the wind energy.”

Future of inconstant electricity supplies difficult to manage otherwise

The relationship between wind power capacity and total capacity is unmistakable. This has been proven by another European country, one with far fewer problems of this sort. Scheepers elaborates: “Ireland is similar to Denmark, where there is also a relatively large amount of wind energy capacity. The big difference is that the Danes can exchange a lot of electrical energy with Norway, which has an abundance of hydroelectric generating stations. Those generating stations compensate for the Danish shortages. But if there’s a strong wind in Denmark, their wind power goes just as easily to Norway and the hydroelectric plants become ‘reserves’.”

Solution for the inconstancy of the wind
Government plans consider the possibility of wind producing up to a third of the electricity supply in the Netherlands. To compensate for the inconstancy, there must be a solution that works as well as the system in Denmark. Scheepers comments: “We already do this to some extent. The Netherlands has an exclusive connection to the Norwegian grid. There is a thick cable on the sea bed between Norway and the Netherlands, through which we exchange power with (hydroelectric) generating stations in Norway. If we want more, we can lay another cable beside the first one.”
Another solution is coupling the wind parks to a larger electricity market, not only looking to Dutch consumers, but to all consumers in north-western Europe. Scheepers explains: “In this region, all of the countries are connected together electrically. For the wind-rich Netherlands, it is important to utilise the existing connections with other national grids more efficiently.”
Here Scheepers refers to the way the national grid managers work. At the moment, the amount of electricity transferred over the electrical cables between countries has to be indicated 24 hours in advance. “For wind park managers that want to send their power abroad, that’s a difficult task. The smaller the number of hours between indicated and actual supply, the more precise the wind power prediction. And everyone profits from that.”

Efficient grid connections
Scheepers believes that we need to think big and look at the whole (European) system. “If a low-pressure system moves through, it is often so big that in terms of wind power the picture is the same for all of north-west Europe. Then the wind turbines from Denmark to northern France all produce a lot of energy at the same time. That electricity needs to be supplied to a big market. ECN studied whether the Netherlands will be able to handle 10 gigawatts of (inconstant) wind energy in 2020 (it currently has almost 2 gigawatts). And it’s possible, as long as there is a reliable wind power prediction and the grids are connected more efficiently.”
The above discussion mainly concerns what power producers can do to compensate for fluctuations. But according to Scheepers, what many people forget is that the power consumers can also make a sizeable contribution. “Produce farmers with a CHP system (combined heat and power; system that produces both heat and electricity) already only turn on their systems when the electricity costs are high. They release the extra heat into their greenhouses, which become a sort of buffer. If there is suddenly more or less wind available, the produce farmers can react to this by turning their CHP systems on or off. A similar ‘synergy’ is conceivable for the pairing of cold-storage warehouses and wind parks. If there is suddenly more wind than expected, the freezers can work harder. The extra refrigeration is the buffer to tide over periods with less supply. In the future, the home freezer could also work this way, if it is fitted with a chip that stays in contact with computers that harmonise the electricity supply and demand. This technology is called PowerMatcher.”

Transmission system becomes exchange system
Whether it concerns producers or consumers, the adaptations fall under the heading intelligent harmonisation of electricity supply and demand. These adaptations need to be realised. Scheepers also predicts that northwest Europe will, in future, be covered by two networks: a high-voltage grid for the transmission of pure electrical energy – which is actually already in place – and a new grid, on which the producers and consumers communicate about supply and demand. The currently existing internet could in theory take on this role. At the junctions of this data network would be the PowerMatchers. They ensure than the correct amount of electrical energy is exchanged. Scheepers adds: “If we talk about cross-border transmission lines, we mean the transmission grid through which generating stations can reach each others’ service area. Originally, these connections were laid to guarantee the electricity supply, but were later used for the bulk transmission of electricity as well. In 2020, this system will have the added task of removing the surplus or shortage of the fluctuating wind parks as efficiently as possible. And then the transmission system will become an exchange system.”

Contact
Martin Scheepers
ECN Efficiency & Infrastructure
Tel.: +31 (0)22 456 4436
E-mail: Martin Scheepers

Information
Click here to view or download the Future electricity prices report, which contains exchanges between Northwest European Electricity markets.
Click here to view or download a report on research into heat pumps that level the production ripples of wind turbines.

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