Nuclear Energy in Denmark
(May 2009)
- Denmark as a political entity can be represented as getting most of its electricity from coal, and a substantial amount from wind.
- The country in fact is not isolated but is part of two major electrical grids which depend on nuclear power for much of the base-load supply.
Denmark in 2007 generated 39.2 billion kWh of electricity gross, 47% of this from coal, 22% from gas and 18% (7.2 billion kWh) from wind. These figures however are artefacts since Denmark is neither isolated nor unified electrically - East Denmark (Zeeland) and West Denmark (Jutland & Funen) are unconnected and each is part of a major grid system. In 2005 about 11.6 billion kWh was exported and 12.9 billion kWh imported - from Germany, Norway and Sweden. The main import is from Sweden and the main export is to Germany.
Energinet.dk is the transmission system operator and owner of the main electrical infrastructure in Denmark. It took over in 2005 from Elkraft in Eastern Denmark, and Eltra in West Denmark. Per capita electricity use is about 6200 kWh/yr.
In 2006 total installed capacity within Denmark was 13 GWe, 9.9 GWe of which was fossil fuel-fired and 3.14 GWe wind turbines, the majority on or offshore West Denmark. The wind turbines depend heavily for their effective utilisation on 27 GWe of hydro capacity in Norway, over 1 GWe of which can be despatched when wind power is unavailable in West Denmark. With good winds, power can be exported back to Norway and there conserve hydro potential. The net import-export balance of electricity with Norway is very variable. In 2002: 0.71 billion kWh net import, 2003: 3.82 billion kWh net export, 2004: 2.30 billion kWh net export, 2005: 4.24 billion kWh net import, 2006: 1.2 billion kWh net export. Robust connection between Norway's hydro turbines and West Denmark's wind turbines holds the key to successful exploitation of wind for Denmark, and the German and Swedish connections are nearly as important.
Trade from West Denmark is through a 1040 MWe DC connector to Norway, a 630 MWe DC link to Sweden, and a 1400 MWe AC connection to Germany. From East Denmark there is a 600 MWe DC connector to Germany and a 1775 MWe AC link to Sweden, total 5.4 GWe (though more recent total is 4.6 GWe).
The power imported from Sweden (1.7 billion kWh in 2006, 7.6 billion kWh in 2005) is almost half nuclear and half hydro, the power (4 billion kWh in 2006, 0.6 billion kWh in 2005) imported from Germany is largely generated by brown coal and nuclear power (Germany itself imports 15 to 20 billion kWh/yr from France, which is 80% nuclear). Norway is almost all hydro.
Hence there is a natural and felicitous interdependence between West Denmark's wind and Norway's hydro. Beyond this there is back-up capacity from both Sweden and Germany, with the potential to export surplus power, notably from wind, when it is available.
Denmark has had a wide range of incentives for renewables and particularly wind energy, accounting for nearly one third of total wholesale electricity prices. Apart from the Purchase Obligation (PO) for renewables providing an effective subsidy, there is a further economic cost borne by power utilities and customers. When there is a drop in wind, back-up power is bought from the Nordic power pool at the going rate. Similarly, any surplus electricity is sold to the pool, though is deemed to be non-PO power. The net effect of this has been growing losses as wind capacity expanded. Official estimates put the expected losses at DKr 1.5 billion (EUR 200 million) per year.
After a thorough review in 2002 of costs and benefits of the country's heavy support for wind power, a new energy policy was adopted in 2003. This modified the previous subsidy scheme for renewables, making it more compatible with the open electricity market and providing incentives for grid companies to maintain reliable and stable electricity supply.
Copenhagen-listed Vestas is the world's largest manufacturer of wind turbines and is valued at EUR 17 billion.
Case study: West Denmark
West Denmark (the main peninsula part) is the most intensely wind-turbined part of the planet, with 1.74 per 1000 people - 4700 turbines totaling 2315 MWe, 1800 MWe of which has priority dispatch and power must be taken by the grid when it is producing. Total system capacity is 6850 MWe and maximum load during 2002 was 3700 MWe, hence a huge 81% margin. In 2002, 3.38 billion kWh were produced from the wind, a load factor of 16.8%.
The peak wind output was 1813 MWe on 23 January, well short of the total capacity, and there were 54 days when the wind output supplied less than 1% of demand. On two occasions, in March and April, wind supplied more than total demand for a few hours. In February 2003 during a cold calm week there was virtually no wind output. Too much wind is also a problem - over 20 m/s output drops and over 25 m/s turbines are feathered. Generally, a one metre/second wind change causes a 320 MWe power change for the whole system.
A report on Danish wind power 2005-07 was appended to a 2008 UK House of Lords report on The Economics of Renewable Energy. It showed that while production of wind power corresponded to about 20% of Danish consumption, much of it in fact exported at very low prevailing prices rather than substituting for domestic base-load coal-fired generation. For Western Denmark, in 2007 wind generation amounted to 25.8% of the total but only 15.8% of internal use. Taking east and west together, wind power consumption for the three years 2005-07 was 13.6%, 10.3% and 13.0% of total consumption. The analysis suggested that for a 400 MWe offshore wind farm, only 36% of output would be used in Denmark and 64% exported at prevailing spot prices. In 2007 there were even 83 hours when the spot price was zero and the exported power was given away.
Early in 2009 Nord Pool announced that from October the spot floor price for surplus power will drop from zero to minus EUR 20 cents/kWh. In other words, wind generators producing power in periods of low demand will have to pay the network to take it. Nord Pool said that "A negative price floor has been in demand for some time - especially from participants trading Elspot in the Danish bidding areas. … Curtailment of sales may give an imbalance cost for the affected seller and thus creates a willingness to pay in order to deliver power in the market." This is likely to have a negative effect on the economics of wind power in the region, since a significant amount of Denmark's wind power production is affected.
R&D
Denmark has had three research reactors, but only one of these now operates: DR-1, a 2kW unit from 1957. Two larger and newer units have been shut down.
Conclusion
Nuclear power provides an essential part of Denmark's electricity. Its high usage of wind in fact depends primarily on imported Scandinavian hydro power especially to West Denmark, and secondly on both East and West Denmark each being part of a major grid system incorporating a large proportion of nuclear power.
Using 2005 data, with production of 36.3 TWh, consumption of 34 TWh, exports of 12.9 and imports of 10.4 from Germany and 0.7 from Sweden, it would seem that 3 TWh used is nuclear, about 9% of total.
References:
OECD/IEA Electricity Information 2007.
OECD/IEA Energy Balances of OECD Countries, 2003.
IAEE Newsletter Q1, 2003.
Eltra & Elkraft, Environment Impact Statement for Electricity, July 2005.
Energinet
參考來源:World Nuclear Association
