a) At present, Denmark has the world's highest concentration of wind turbines per head of population. Its 5,267 turbines (3.126 GW installed capacity) produce the mathematical equivalent of almost a fifth of the country's annual demand for electricity, yet at the moment of its generation, only about one-third of this wind electricity (equivalent to the output of about 1 GW of installed wind capacity) can be used within national borders. In 2005, only about 6 percent of the country's annual demand for electricity was supplied directly from this source, and this needed the continual backup of conventional fossil-fuelled generators.
b) Most of Denmark's annual production of wind electricity has presently to be exported (at considerable economic cost) in order to secure the operational integrity of its conventional power transmission systems. This surplus is transferred to the grid systems of Norway, Sweden and Germany via international connectors (5.19 GW capacity) big enough to take the total output of the country's wind carpet. Relative to average electricity demand, this capacity is about 25 times that of the UK, and without it Denmark would face serious difficulties maintaining the integrity of its grids and disposing of its large surges of wind power.
With its much lower capacity of international connectors and fewer ‘storage' facilities, the UK cannot achieve comparable proportions of wind power penetration. Its electricity demand is about ten times that of Denmark, so without a massive re-build of infra-structure and inter-connectors, serious transmission problems may be expected to surface once the installed capacity of wind turbines reaches about 10 GW. This estimate is virtually identical to the maximum of 10 GW wind power capacity proposed for the UK in a more comprehensive study published in 2005 ( 67).
c) To resolve its present transmission problems and avoid the expensive generation of surpluses, Denmark is examining the opportunistic use of excess wind power for the resistance heating of water at district heating plants. It is also considering the manufacture of hydrogen as a fuel carrier. Both approaches appear feasible, albeit at considerable extra cost.
A more holistic long-term project aims to re-structure the whole transmission system, and fully integrate wind power with gas-fired local CHP plants in highly automated ‘cells'. It is predicted that these cells will operate as independent, adjustable, virtual power plants controlled by regional and national control centres. Major weaknesses of this approach are its high cost and operational complexity, and the long-term commitment of Denmark to potentially insecure supplies of natural gas (methane is itself an important greenhouse gas).
Only time will reveal the economic and technical feasibility of these approaches and, more especially, their potential to conserve fossil fuels or reduce carbon emissions in the holistic context. The Administrative Director of DONG Energy (Denmark's biggest player in the wind turbine market) has commented : "[In the foreseeable future, wind power cannot solve the energy problem because it is too unstable and perhaps too expensive]" ( 68). Vattenfall's Head of Information suggests that it is unrealistic to imagine that wind power can overtake other forms of energy within the next ten years ( 70). In any event, the irregular supply of wind power will continue to challenge the efficient operation of gas-fired backup plant.
d) In the highly politicised, commercial environment of wind technology (in which politicians are seeking to make Denmark a ‘Shop Window' for their product ( 31; 39)), many Danes fear that the aesthetic quality of their countryside and wilder regions will continue to deteriorate as cherished landscapes, seascapes, and wildlife habitats become dominated by ever-taller wind turbines, with their associated access roads, pylons and cables. At the local level, opposition has already grown to a level at which national politicians are having to put pressure on Municipalities to find sites for bigger turbines.