Updated: Aug 24, 2021
Over the past decade, prices for Solar PV Plants have reached an all-time low, leading to thousands of GW being added to the energy generation worldwide. But, the sun ain't always shining! Installing an on-grid plant is an optimum solution when you can consume all the generated energy then and there itself. The net-metering scheme gives the benefit of storing energy for the end-users, but in the end, there is someone who has to pay the price for storage and in the case of net-metering it is the DISCOM. To firm renewable energy in our system, that is to ensure there is always energy on demand no matter the time of day or what weather it is one of the biggest challenges in the industry. We need to store the renewable energy for use later and the main option right now is limited to lithium batteries which are used in Tesla's Powerwall for home or utility storage solution Powerpack. Now, although the price for lithium batteries is dropping year on year, experts say the price will remain too expensive for utility-scale applications. To get to a utility level storage, the price point needs to come down to nearly 20 times than it is right now for lithium batteries. Plus they pose a fire risk over time as per usage.
To address this issue, there is a cadre of entrepreneurs who are working to commercialize energy storage most innovatively which has serious potential.
From 2010 to 2020, installed capacity for renewable energy has increased from 10milion GW to 27million GW! And this is not stopping here, renewable energy is expected to grow 50% over just the next 5 years!
Solar PV is today the cheapest way of generating energy since China flooded the market with cheap photovoltaic cells since the 2010s. And along with this, so has lithium batteries have been becoming cheaper with costs falling by 85% since 2010. Currently, solar or wind farm in combination with lithium-ion batteries is the cheapest form of energy storage option, cheaper than the peaker plants. Tesla currently has installed the world's largest lithium-ion battery bank on a utility level in Australia paired with wind turbines and is in process to install another 300MW sized storage solution in Australia. But this solution is not workable financially for the billions of smaller-scale applications like residential or small-scale industries.
Let us take a look at other solutions in this field.
Flow batteries: One of the main alternatives that are being considered is flow batteries. Unlike lithium-ion, they store the electrolyte in external tanks providing with much lower fire and capacity fade risk.
California-based Primus power is working in this field. The modular solution from Primus power can provide 25kW power for up to 5 hrs, enough to power 5-7 homes for 5 hrs. Also, ESS Inc is another company working in this sector. Their solution is primarily battery banks in shipping containers with the ability to provide from 100kW for 4 hrs to 33kW for 12 hrs and use the electrolyte purely of iron, salt and water bring down the cost phenomenally. It is also in the process of developing an energy center, a utility-scale operation in a 100MW+ range!
Gravity-based storage: Peaker plants have two reservoirs, one on a higher elevation than the other. When there is excess energy in the grid, it used the energy to pump the water in the higher elevation tank, and when there is an energy demand it simply allows the water pumped in the reservoir above to flow down generating electricity using turbines. Similarly, gravity-based solutions use dead weights instead of water which reduces the footprint of the project and can function in any geography.
Energy Vault is a company working in this field. It uses 35ton weight bricks to bring them up and down generating energy when lowering depending on energy needs. A standard installation of 20 towers of bricks can provide with 350mWh of electricity enough to power 40,000 homes for 24hrs! The company is currently building a test facility in Italy as well as a plant for TATA Power company. However, the energy density in these systems is very low.
Thermal Storage: This is still a very new and emerging field but has the potential to store energy for a longer period than flow batteries and with a smaller footprint. California-based Antora Energy is working in this field. When there is excess energy in the grid that is used to heat the carbon blocks which are insulated inside a container. Then, the heat is converted back to electricity as and when needed. Typically turbines are used to generate electricity from heat but that is the major change in this storage technology. Antora has developed a novel thermophotovoltaic heat engine or TPV which are like solar cells, just these cells capture the heat radiated out from the heat source and convert that to electricity instead of light. And the fact that the heat is stored in ultra-cheap elements till used, brings down the cost of this type of storage considerably.
Other than these storage methods, multiple others are being tried out. Toronto-based Hydrostor is experimenting with the storage of compressed air underground to be converted to electricity later. Or the US-based Highview power is experimenting with cryogenic storage that is using excess energy to cool down air up to a point it becomes liquid.
All these ideas seem far out in the future, but investments are pouring in and projects are being piloted all over the world. Overall the energy storage market is expected to attract 620million dollars in investment by 2040!
When we can store about 20% of the peak demand in these storage solutions, we would be able to run a renewable-only system that can carry us through those potentially long lulls
Though which technology or company will have an outbreak is impossible to figure out right now, for renewables to better compete with fossils fuels, we need to figure out a way to better store energy!
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