The myth of 100% renewable electricity

Welsh Government policy is to increase the country’s generation of electricity from renewable sources from 59% of consumption at present to 100% by 2035. This target is to be achieved predominately by an increase in wind and solar capacity. The policy ignores issues of fluctuations in demand, intermittency of supply and basic economics.

Definitions

Demand is how much electricity a system requires at a single moment in time. It is measured in megawatts (MW). Generating capacity must be capable of meeting demand at all times.

Consumption is how much electricity a system uses over a period of time. This is measured in megawatt-hours (MWh). If demand were constant at 1 MW, annual consumption would be 1 X 24 hrs X 365 days = 8,760 MWh or 8.760 GWh pa.

Capacity factor or load factor is the relationship of actual generation to total potential generation based on the rated capacity of the project.

Demand and consumption

Electricity consumption in Wales is presently 13,000 GWh per annum. Demand varies between 1000 MW on a summer day and 2300 MW on a winter evening. Consumption is forecast by the Welsh government to increase to 29,000 GWh per annum by 2035 with demand varying between 2500 MW in summer and 4500 MW in winter

At present Wales has 3,551 MW of renewable generation capacity (2/3rds wind, 1/3rd solar) producing 7,720 GWh of electricity per annum, approximately 59% of consumption. The low rate of generation vs capacity (24%) reflects the low capacity factor on wind power at 30% and solar at 10%. To meet its 100% target for 2035 the Welsh government estimates that renewable capacity will need to be increased by 8,500 MW to 12,000 MW. Because of the long lead times they say this would require significant new onshore and offshore wind projects to begin development in the next 5 years.

Problems with 100% renewable target

Fluctuation of demand - demand varies according to the time of day, the season and with consumption events (e.g major football matches etc.) In order to meet fluctuations in demand it is necessary to be able to vary generation. This is possible with easily controlled systems such as gas but not with weather dependent renewables.
Intermittency of supply - Variations in weather conditions influence the generation of energy from wind and solar systems. On calm overcast days there may not be sufficient generation from renewables to meet demand notwithstanding capacity and it would be necessary to rely on a back up system such as gas or nuclear or to import energy. Simply increasing renewable capacity would not overcome this problem and on windy sunny weather would result in a significant over supply.
Economics - Wales is a small country within a large weather system. High pressure systems lead to periods of settled weather that cover the whole of the UK. During these periods when supply from wind generation is limited in Wales it would also be limited elsewhere in the UK and neighbouring continent. With an over reliance on weather dependent renewables Wales would find itself in competition for limited supply from other sources to meet demand resulting in unsustainably high import prices whether from additional fossil fuel or nuclear generation or inter-connectors. Conversely low pressure systems with high winds over the UK would result in an over supply of wind energy which it would be difficult to export at economically viable prices and in many cases lead to constraint payments being made to wind generators to shut down production. In summary incorporating a significant intermittent component in a grid will typically result in the trading equivalent of buying dear and selling cheap - the opposite to what is desirable. Increasing the intermittent element would simply exacerbate this.

Solutions proposed by Welsh government

Equivalence - for the reasons above it is not practical or economically viable to have an energy policy based on 100% renewables. In order to overcome this problem whilst meeting its target the Welsh government has proposed the fiction of Equivalence. The idea is that the target may be met by matching imports of fossil and nuclear energy with exports of renewable energy. This is clearly at odds with public understanding of 100% renewables as promoted by the government and also ignores the economic viability of a policy of selling during a period of surplus and buying during a shortage referred to in 3 above.
Storage - Supporters of renewable energy tend to talk about development in battery storage as the solution to the intermittency problems but ignore the amount of storage that would be required, the cost, the environmentally damaging materials required in production and the fact that any significant advances are many years away. Battery storage capacity is measured in MWh. It is estimated that to store one days Welsh surplus from a sunny and windy summer’s day for later use would require around 90 GWh, equivalent to approximately 1.5 million electric car batteries. A more efficient but costly, and therefore unlikely, storage solution would be to build a further 10 pumped storage reservoirs similar to Dinorwig. A further suggestion is that the surplus electricity could be used to generate green hydrogen but the energy loss on the process of Electricity->H2->Electricity would mean that it would be a very inefficient as a storage system and certainly no reason for building surplus capacity.

Summary

100% renewable electricity by 2035 is simply a sound bite put out by a government more interested in virtue signalling than in dealing with the practicalities of ensuring a reliable supply. The danger is that they will believe their own words and aided and abetted by foreign investors will destroy large areas of our countryside and environment in pursuit of a flawed policy.