In Great Britain, electrical power is supplied via the National Grid, which constantly and carefully balances supply against demand. This is a vital and high-stakes process—deviations of more than 1% in the Grid’s conditions can lead to infrastructure damage and power outages due to blown fuses. (Even deviations of less than 1% will have noticeable consequences to the discerning clockmaker).
The demands on the Grid are ever-changing and difficult to predict at times. Some trends can be predicted—most people would probably expect demand at 2am to be lower than 2pm, and they would be correct. But what about weekends? Will they cause demand to increase—since more people are in their homes using power—or decrease—since offices are mostly sitting empty? How about a public holiday? On Christmas Day is there a sudden peak in demand, as every oven in the country is switched on, or a drop as the shops all close? (If you’re curious, I’ve put the answers to these questions at the bottom of this post.) And, of course, here in England, during major football matches there is a spike in national energy demand at half-time, as everyone puts on their kettle.
The National Grid has been around for some time and is good at predicting such fluctuations in demand, but that only gets them half of the way there. Once they know what the demand will be, they must then supply that amount, constantly supplying more or less electricity to fuel our tea-drinking, football-watching and Christmas-turkey-roasting activities.
In the world of burning fossil fuels, varying the supply was relatively simple, with a procedure along the lines of ‘burn more gas when we need more power’. It is slightly less straightforward to carry out the procedure ’make it windier when we need more power’ or potentially ‘increase sunniness during periods of high demand’.
This is, of course, an exaggeration of the problem, as some sources of renewable energy are easy to control, for example hydro and biomass. However, only 30% of renewable electricity is currently supplied by those sources—the UK largely relies upon the more unreliable wind, wave and solar energy. So we’re still left with the issue, how can we control the power that comes from these intermittent sources?
A simple, but inefficient, solution is to have the capacity to produce way more energy than we need, and then just turn on and off solar panels/wind turbines as we need more or less power. It works—but there has to be a better way.
There is—we can store the excess energy produced on sunny, windy days to use on cloudy windless days. The most common way of storing energy in Great Britain at the moment is PSH——pumped-storage hydroelectricity—since it’s very efficient. When there is excess energy, water is pumped to a height. The water is then allowed to fall through a turbine at a later date when the energy is needed back. Using this, we can control the power from unreliable sources.
We can also alter the demand on the Grid at times when the supply is falling short, for example by using Demand Response Management. This involves lowering the demand on the Grid at peak times by taking some large users off the Grid. These users are usually banks or hospitals, who keep generators on site in case of power failure. When demand on the Grid is high, the Demand Response Aggregators simply ring up these users and ask them to turn on their generators (for a fee), thus taking demand off the grid temporarily.
So, with investment in infrastructure, such as the above method of energy storage, the UK could run on 100% renewable energy. This is of course a technical analysis of the possibility, ignoring political, economic, and other factors. Still, it’s promising to know this could be possible.
Answer to the question—weekend and weekday demand is basically the same, and public holidays have lower demand.