It is expensive and often impossible to regulate renewable generation according to demand: the level of wind power generation, for instance, will have to follow the present wind speed. An important exception is hydro power, which uses reservoirs to store the water. 

Other forms of CO2-free power are also less flexible than traditional fossil fuel-based power.  Converting to power generation with lower emissions of CO2 therefore presents many challenges for the power system.

Differences in flexibility
Nuclear power can in principle be regulated, but such regulation is expensive. Nuclear power stations have high fixed costs and low production costs. Once they have been built, it is therefore more efficient for them to generate power most of the time. In the case of wind power, wind farms have virtually zero operating costs, so the aim is to generate as much power as the wind permits. Small-scale hydroelectric power stations do not normally have an associated reservoir and must therefore generate power based on inflows. Solar energy generates power in proportion to the amount of incoming solar radiation.

Combined heat and power stations (CHP), use the waste heat for heating purposes, so increasing the overall energy efficiency substantially. However, in order to achieve this high efficiency, power generation must largely follow the demand for heating, rather than the demand for electricity. Power that is generated using biofuel has a low proportion of power and a high proportion of heat. In the case of such power stations, there will therefore be even more reason to generate power and heat together, in order to achieve a high efficiency. The more sensitive the pattern of power generation is for the demand for heat, the less flexible power generation.

Power stations with CO2 capture and storage (CCS) require major investment. Once investment in CO2 capture systems has been made at a power station, it will be economically sensible for the power station to operate for much of the time, while power stations without such cleaning systems cover the peaks in consumption to a greater degree.

The above examples illustrate the differences between different forms of CO2-free power:

• Nuclear power and power stations with carbon capture have a cost structure, which is appropriate for continuous production.
• Combined heat and power (CHP) production is strongly influenced by the demand for heat.
• Wind power, small-scale hydroelectric power and solar energy are dependent on the weather conditions.

Common to them all is the fact that the costs associated with regulating production are greater than the costs associated with regulating traditional fossil fuel-based power. Adjustable hydro power is to some extent an exception from this picture.

Trade with other countries
Hydroelectric power stations with reservoirs have very good regulation capacity over an hour or day, or even over up to several months. This is valuable. However, in the long-term, hydroelectric power cannot produce more than the quantity of energy permitted by the inflow (precipitation). Hydroelectric power is therefore itself dependent on the energy flexibility of other power producers or of consumers in order to balance out the substantial variations in inflow between dry and wet years. As Norway has very little energy-flexible power generation and consumption is not particularly flexible, international trading represents an effective tool for coping with large fluctuations between wet and dry years.

Norway needs new and stronger links
Nordic coal-based power has been important in compensating for the fluctuations in inflow to the hydroelectric power stations and coal-based power will continue to play such a role for many years to come. With a more ambitious climate policy, the proportion of coal-based power could however gradually be reduced. There is thus a need for other possibilities for balancing the supply of energy within the power system. The most obvious solution is for Norway to establish stronger links with countries outside the Nordic region, such as Germany, the Netherlands and Great Britain. This would help the new trading partners with regard to short-term balancing (day/night) and present Norway with more opportunity to import during dry years and export during wet years.

Local and district heating
One of the few areas, which could contribute by providing more consumption flexibility in the future, is represented by installations for local and district heating. The heating processes in such systems can for example be easily switched between bio-fuel and electricity. During periods with low renewable power supplies, bio-fuel can be used, while during periods with a large surplus of renewable power, the power that is generated can be used for heating purposes.  This ensures the good utilisation of power even during periods with high inflow rates and high winds. The potential for this type of flexibility is greatest in our neighbouring countries, because they have well developed district heating networks.