Renewables & Energy Storage

A match made in heaven?

A common complaint about renewable energy sources is the unpredictability, so an integrated solution with energy storage is highly attractive on the face of it.

It is hard to argue too much with the unpredictability aspect of renewables; predicting the wind, is challenging, no doubt. Waves are slightly easier to predict as they tend to lag behind the wind, giving you some notice prior to the incoming swells. Tidal is very predictable, but does not necessarily produce energy when there is a need for it. And when is it ever sunny when you want it to be?! Therefore, in order to better match the demands of a population, a combination with energy storage infrastructure would work well to provide energy from renewables when it is needed.

There are many means for storing energy, including (but not limited to):

  • Displacing a mass or a fluid (linearly or angularly) - potential or kinetic energy
  • Thermal storage - thermal energy (kinetic energy at an atomic scale)
  • Batteries - chemical energy
  • Capacitors - chemical energy

All of these have their different ideal applications and loss rates over time. As with renewables, we don' think there is a "one size fits all" solution here. For example, capacitors (or more likely ultra-capacitors) are good for short term storage and discharge, which could help smooth the peaks in wave energy, while displacing a large mass during a tidal flow in the middle of the night would allow that energy to be released as the demand rises in the morning. Different storage options are better fits with some renewable energy technologies than others and will be dependent upon the locations they are providing energy to.

Renewables and energy storage

Displaced Mass Storage Figure Source: Gravitricity

Renewables & energy storage

Perhaps the most intriguing option we have seen recently is a combination of multiple emerging technologies - renewables, energy storage and electric vehicles. An electric vehicle is - simply put - a big battery on wheels that is stationary for 95% of the time. Seeing as these large capacity batteries are being produced already could they be dialed into a smart grid system to act as useful energy storage vessels?

The potential impact of ignoring this opportunity and not integrating electric vehicles into a smart grid system is significant. There would be a huge peak in demand as everyone got home and put their vehicle on charge; this would be incredibly hard to meet and to manage on a daily basis. Instead, owners should be encouraged to plug their vehicles in whenever they are stationary in order to take advantage of the smart grid potential. In this way cars could be charged during the day when they are not in use and they can store the energy being produced by renewables (dependent on the conditions). This allows renewable sources to be used effectively and the energy stored in vehicles for later use - in the evening peak for example.

There is the question of quite how you get people to always plug their vehicles in wherever they are; challenging from both an infrastructure and an incentive point of view, but who said it was going to be easy? There is a lot of political momentum behind tackling climate change and improving air quality and that will help pave the way for solutions like this. For more information around this topic see the IMechE Professional Engineering article here.

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