The future of electricity is now! Well, not really… but it’s fun to think about anyway
In a world where our governments have finally started to care about serious greenhouse gas emissions reduction and are actually working to significantly increase the share of renewables in our electricity mix (and people might have finally found a different phrase for introducing futuristic, fantastical and/or far-off scenarios), there are, as you might have guessed, even more challenges to tackle than just replacing fossil fuels. Because sadly, 1 MW of solar or wind isn’t the same as 1 MW from a coal plant. What I’m talking about here is the issue of system balancing: making sure that electricity supply meets demand at all times.
Supply and demand: base & peak load
First, a general introduction to the workings of our electricity system. The minimum demand for power over some time span is called the base load, on top of which additional demand fluctuates, peaking at certain times a day.
Now, electricity supply is built up in a certain hierarchy: first there’s the base load power plants. These are the cheapest to keep running (which is linked to their generally high efficiency), and they are relied upon to supply a constant power output near their maximum capacity to meet our minimum demand. They rarely shut off and are typically inflexible: it takes a while for them to get started and their output is best kept constant. Nuclear fits this role perfectly, and coal is also usually used for this purpose. The variable demand on top is then taken care of by more flexible technologies; this can be done by load-following, where a plant adjusts its output throughout a day to account for changes in demand, and, in times of especially high demand, by peaking power plants, fired up just to help cover the peaks. These latter services are traditionally provided by gas-fired power plants.
The problem comes with intermittent renewables, namely solar and wind, whose power production is unpredictable (especially in the case of wind), and over which we have no control. If these technologies end up forming a large share of our generating capacity, extra efforts will be needed to compensate for e.g. the lack of sun at night or a sudden change in wind; different options exist on either the supply or the demand side.
Supply: flexibility and storage
Hydroelectricity, when designed with a reservoir, can fulfill all roles on this side, since it’s highly flexible: the output can be controlled by letting more or less water out through the turbines, and the contents of the reservoir can be saved for when a peak occurs. Biomass-fired and geothermal plants can, to some extent, also be manipulated to meet varying demand. However, increasing the frequency of switching a plant on and off generally heightens the maintenance costs, and operating a plant at lower capacity often has implications for the conversion efficiency. Alternatively, we can look to energy storage methods to help us cope with the variability in supply and demand. Examples include pumped hydro storage, in which unneeded energy is used to pump water to a greater height, to be released through turbines when demand rises (which could be combined easily with reservoir hydro power) or battery storage.
Demand: smart grids
On the demand side is where things get most interesting though. The leading concept here is demand response: customers adjusting their power consumption based on the price of electricity. This works even better in a smart grid, where household appliances connected to the grid automatically receive information about the price of electricity, and depending on the customer’s preference, are able to adjust their functioning on the basis of this information. For example, you could set your dishwasher in the evening to only start when the price drops below a certain level. All that matters to you is that it’s done in the morning, but the result of this system is that you washed your dishes the cheapest way possible, and your demand coincided with a moment when there was a lot of wind, or overall demand was especially low, etc., thus helping to match up supply and demand.
The higher the “electrification” of households, the more exciting applications come to mind: take electric cars, which we expect to be seeing a lot more of in the future. From a grid operator’s perspective, a fleet of electric vehicles is little more than a large battery bank when they’re hooked up for charging. You could imagine setting your electric car to a “smart charging” setting, in which it charges when overall demand and therefore the price is low, and it returning some of its energy when demand is high, making you a temporary supplier. Such a system could straightforwardly include distributed generation (e.g. solar panels on people’s rooftops) as well.
Before we get too starry-eyed with near sci-fi innovation though, it’s important to remember that we’re in no way close to something like this on a large scale, and a lot will have to happen, politically, economically and technologically, before smart grids become a reality. Most importantly, we need to drastically decrease our dependence on fossil fuels. When that scenario doesn’t seem quite so far-off anymore, perhaps we can justifiably say that the future of sustainable electricity systems is, indeed, now.
Additional sources & further reading
- https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_chapter7.pdf, section 7.6.1