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What could a renewable city grid look like?
There is certainly a greater awareness of climate issues and the need to look to renewable resources for energy generation, rather than fossil fuels that release large quantities of harmful CO2 emissions. Most people are in favour of renewable energy generation for our burgeoning cities.
Some may say that renewable energy is not something new. Why are we only now starting to explore it as a viable alternative to fossil fuels on a larger scale? One of the reasons is that for many years the development of a renewable energy infrastructure was held back by the concern that wind and solar energy was too variable therefore too unreliable to tie into the grid. This theory, not surprisingly, was perpetuated by the fossil fuel industry looking to protect their interests. However, this myth has been busted as engineers and innovators have found viable solutions for creating more stable integrations and energy storage solutions and proving that renewables can be an effective and reliable alternative energy source.
Given the government’s commitment to reducing carbon emissions and reliance on fossil fuels, the industry was forced to look for ways to make renewable energy work so that it could tie into the grid system effectively. Simply saying it couldn’t or wouldn’t work was no longer an option. Especially with the ambitious net zero emissions targets that have been set.
It has helped that there has been considerable investment in developing wind and solar farms and the capacity being generated is tipping the economies of scale in favour of renewables. However, the primary challenge of renewables remains energy storage.
The one major drawback to renewable energy is that it is often most needed when it can’t be generated. For example: There is a far greater demand for energy for heating when it’s cold, wet and dark and the sun isn’t shining. Wind generation also depends of prevailing weather conditions with minimum wind speeds in order generate a certain capacity that can be exported to the grid. Finding an effective energy storage solution is one that many engineers and innovators have been working on.
Location too is another challenge to overcome, because of the size of windfarms and wind turbines they are often located offshore or in more remote locations. This means that the energy generated has to be transferred a fair distance to reach the cities.
To date the default has been to store energy generated from renewables in Lithium ion batteries, very effective for smaller installations, but not always practical when looking to supply a grid. Batteries also have the downside of having a limited lifespan and can be hazardous if damaged or not recycled properly. So the question remains: Is there a more sustainable solution for mass energy generation and storage?
Renewables innovation – applying proven concepts
While solar is very effective in supply industry during daylight hours, a major drawback is that households typically require energy at night for cooking, heating and lighting. Some US university scientists are working on a way to recover the earth’s thermal energy at night through heat capture and use this to power homes at night. If this could be rolled out on a major scale, it could prove to be a very effective solution.
But that still doesn’t really solve the issue of energy storage capacity for a city grid. While individual home solar systems can be easily linked to lithium ion batteries, this requires individual system installation at each location which is then tied into the grid. A good concept if home owners can afford the solar PV systems but limiting if they cannot. Some investors have come up for a solution to this creating a financial model whereby they generate capital for the installation through investors and then the homeowners can lease a solar PV system that feeds back into the grid. There is a dual benefit to this concept. Cities can generate needed capacity for commercial daytime use without having to store or transport the energy large distances. Homeowners can benefit from having solar PV system at an affordable rate, often cheaper than buying electricity from the grid. However, we all know that subsidised initiatives eventually run out and those in later benefit less than early adopters.
What we may see more of as renewable grid systems expand is the use of flow batteries. While flow batteries operate similarly to other battery types the main difference is that they are scalable. The capacity is really only dependent of the size of the tanks that the charged electrolyte is house in, so for a greater capacity the tanks simple need to be enlarged. While not a new concept, up until now it has had very limited commercial application. However, several US companies are creating prototypes for experimentation with renewable grid tie solutions.
Another solution which is not new, and has be underutilised, is compressed air energy storage (CAES). While specialised storage facilities can be built, one of the most effective applications is making use of old mine shafts (with some adaptions and modifications) to store energy using compressed air systems. This method has the benefit of being clean in that it does not use any toxic chemicals and doesn’t create any toxic waste. Plus using old mine shafts makes it relatively inexpensive. CAES typically can accommodate a large capacity so is ideal for energy storage for a city grid.
It will be interesting to see what other innovations and applications to existing technologies can be made as we seek to develop a fully renewable energy grid.