The net-zero movement and many advanced-country governments are keen to press-on with an electrical revolution, backed by a further major expansion of wind and solar power. The wish to move away from Russian oil and gas in a hurry has increased enthusiasm for this transition.
But why hasn’t renewable power already taken a higher share of the energy market? Why does renewable electricity still only account for around 5% of the world’s total energy supply?
One of the main difficulties for wind-power advocates is to answer the question: What does a country do if it has plenty of wind turbines, but the wind does not blow? What does it do when the wind blows too much – and the turbines have to be stilled? Similar questions swirl around solar when the sun does not shine, or when the hours of night lengthen.
The cost of providing backup
To date, the main practical answer has been to keep enough fossil-fuel generating capacity available to replace the lost wind or solar when the weather lets you down. This gives rise to issues of how you attribute the costs of the backup to the total costs of providing the renewables. It leads to debates as to whether electricity users pay the extra costs of back up, or whether there should be renewable subsidies out of general taxation? Or does there needs to be a balancing payment mechanism across all energy forms?
One way or another, the public needs to pay to have back-up capacity and the providers of that capacity need remuneration for making it available. It clearly entails higher unit costs for these businesses, as they cannot run their plants for substantial periods of time when there is enough wind or sun.
Some think we will need a “green-hydrogen” economy.
A longer-term – and more cost-efficient – answer is likely to entail ways of storing the electricity wind and solar can generate and release it at times of little weather-generated power. Some think the answer lies in large battery stores, though there are losses of power through storage. Some think we will need a “green-hydrogen” economy. If surplus wind electricity can be used to produce large quantities of hydrogen this power source could then be used as direct fuel for heating, industry and vehicles or it could be burned in a power station on windless days to convert it back to electrical energy.
Once again there will, of course, be energy losses through these different transformations. The technology exists both to make the green hydrogen and to build vehicle engines, home-heating systems and industrial-process machinery that can use hydrogen as the fuel. Some think hydrogen fuel is a much better answer than attempted conversion of ships, trucks and heavy plant to electric drive. There is also the possibility of putting in more pump storage systems, where excess renewable power can pump water up hill to be released when there is more electricity demand at higher prices or when the wind has dropped.
Demand management matters too
Others point out that we will also need much greater demand management to handle the large variability of renewables. If people could be persuaded to run their washing machines and dishwashers overnight, they could be offered cheaper night-time wind power. This will require flexible tariffs and smart controls on machines to avoid the need to get up in the middle of the night to supervise the cash-saving uses. As electric vehicles become more common, they will need to be guided to a night-time recharge as the power demands they create will be too great for domestic cable systems and current generating capacity at times of day when families want to use lights, TVs, cookers and other domestic appliances. Some think the electric car could be plugged in to provide battery-based electricity to the household at peak times, to be recharged overnight when national demand drops away.
When evaluating renewable investments, analysts need to be aware of the accounting and public policy treatments in each jurisdiction involved, as there can be significant differences of outcome from different cost, subsidy and tax regimes. The supporting technologies of battery storage, hydrogen conversion and pumps storage need to catch up with the provision of windfarms so that more usable energy can be captured and exploited. The green investment movement is likely to intensify its actions to resolve the issue of how you can make full use of wind and solar energy and smooth supply to meet demand.
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