Is It Worth Storing Solar Energy?

Storing solar energy can be worth it for some applications and situations, though the economic and technical feasibility depends on the specific use case. As solar energy continues to expand globally, energy storage is becoming increasingly important to overcome intermittency and provide power when the sun is not shining. This article will analyze the pros and cons of solar energy storage, economic considerations, environmental impacts, new innovations and case studies to assess whether it is worth investing in batteries or other storage technologies to store solar energy.

What is solar energy storage?

Solar energy storage refers to technologies that store energy from solar panels for later use. There are two main methods of solar energy storage:

Battery storage – Excess electricity generated from solar panels charges batteries during the day. The stored energy in the batteries can then be used at night or during cloudy weather when solar panels are not actively generating electricity. Popular battery types for solar storage include lead-acid, lithium-ion, and flow batteries.¹

Thermal storage – Solar thermal collectors absorb heat from sunlight to warm up a storage medium like water or molten salt. The stored heat can later be used directly for hot water needs or to drive a generator to produce electricity. Thermal storage allows solar energy to be used even when the sun isn’t shining.²

Benefits of solar energy storage

Solar energy storage offers several key benefits that make it advantageous for homes and businesses. One major benefit is smoothing electricity supply and reducing peak demand strain on the grid. Battery storage allows solar energy generated during the day to be stored and used whenever needed, including evening hours when electricity demand spikes as people return home from work (Sandbar Solar). This helps reduce strain on electric grids during peak usage. Additionally, by drawing from stored electricity during these high-demand times instead of the grid, less electricity needs to be generated overall.

Solar batteries also provide emergency backup power in the event of grid outages. Battery storage creates electricity independence in these situations when the grid goes down for any reason. Homes and businesses with solar storage can continue to utilize solar energy stored in batteries to power critical loads when grid power is lost (Go Green Solar). This provides energy resiliency and reduces reliance on backup generators which may run out of fuel.

Overall, solar energy storage allows greater utilization of clean, renewable solar power by time-shifting solar energy to be deployed whenever needed. This provides grid stability, reduces peak demand strain, and supplies emergency backup power.

Downsides of solar energy storage

While solar energy storage offers many benefits, there are some notable downsides to consider. One of the biggest is the high upfront costs of purchasing and installing a solar battery system. The batteries themselves can cost anywhere from $5,000 to $20,000 depending on the size and capacity needed. This is a significant additional expense on top of the already substantial costs of installing solar panels. Many homeowners find the economics challenging even with financial incentives. Battery storage systems also require dedicated space for installation, both indoors and outdoors depending on the type of batteries. This can limit options for homes with space constraints.

There are also efficiency losses from storing energy versus direct use from solar panels. Batteries themselves discharge some energy when charging and discharging, and the process of converting DC solar electricity into AC household electricity also wastes some energy. According to one analysis, these losses can amount to 10-20% of the initial solar energy generated. So while solar batteries enable energy to be used when the sun isn’t shining, some energy is lost in the process.

Economic feasibility

The economics of solar energy storage depend greatly on the scale and application. For homeowners adding storage to an existing solar system, the payback period is estimated at around 10 years (McKinsey, 2016). This is due to the high upfront costs of home batteries like the Tesla Powerwall. However, adding storage can provide resilience during power outages. For utilities, grid-scale storage to smooth renewable output offers more favorable economics with a potential payback of just 2-4 years (SP Global, 2021). This is helped by rapidly declining costs, especially for lithium-ion batteries. Utility storage can also access additional revenue streams from energy arbitrage and ancillary services. At the commercial level, solar+storage is economically viable for companies with high demand charges or that suffer financial losses from power outages. The payback is often between 5-8 years (RMI, 2017). Overall the economics are becoming increasingly favorable for energy storage across sectors.

Environmental impact

Solar energy storage systems have substantially lower lifecycle greenhouse gas emissions compared to fossil fuel alternatives. According to a 2022 study published in ScienceDirect, the average solar PV system has a carbon footprint of 41 g CO2 eq/kWh over its lifetime, compared to 950 g CO2 eq/kWh for coal power and 490 g CO2 eq/kWh for gas power (https://www.sciencedirect.com/science/article/abs/pii/S0306261922003403). The greenhouse gas payback time for solar PV systems is 1-4 years, after which they provide carbon-free energy for the remainder of their 20-30 year lifespan.

Research from the National Renewable Energy Lab confirms solar PV lifecycle emissions range from 30-50 g CO2 eq/kWh, compared to around 1000 g CO2 eq/kWh for coal and natural gas electricity in the US. Solar PV was found to have far lower emissions than these fossil fuel sources as well as nuclear, biomass, and hydroelectric power (https://www.nrel.gov/docs/fy13osti/56487.pdf). Overall, studies consistently show solar energy storage has around 10 times lower carbon emissions compared to coal over the full product lifecycle.

New technology developments

Researchers are making advancements to improve the efficiency and lower the costs of energy storage technologies. Efforts are focused on improving existing battery chemistries like lithium-ion as well as developing new technologies.

Lithium-ion batteries currently dominate the storage market, but new lithium-based chemistries like lithium-sulfur offer higher energy density and lower costs. Companies like Sulfurcell are commercializing lithium-sulfur batteries with 70% lower costs than lithium-ion.

Flow batteries like zinc-bromine offer advantages like decoupled power and energy ratings. Startups like ESS are developing new flow battery chemistries with longer life cycles. Gravity-based storage from Energy Vault uses crane systems and concrete blocks to store energy with low costs.

Continued research and development is driving down costs for both existing and emerging storage technologies to make solar energy storage more affordable and efficient.

Case studies

There have been several successful implementations of solar energy storage around the world. According to a study by IRENA, a 500 kW/500 kWh lithium-ion battery system was installed in Germany to support a household solar PV system. The battery charges during the day when solar production is high, and discharges in the evening to meet peak demand. This has allowed the household to increase self-consumption of solar power from 30% to 60% (source).

However, some solar storage projects have also faced challenges. Stem, an energy storage company, worked on a project in Southern California where the battery system was underutilized due to limited control over the site’s energy use. This highlighted the need for better software optimization to maximize solar self-consumption (source).

Overall, case studies show that with proper design and optimization, solar storage can successfully reduce electricity costs and increase consumption of renewable energy. But failures can happen if the system is not well-matched to the site’s load profile.

Future outlook

The future looks bright for energy storage. According to research from the Massachusetts Institute of Technology, the global market for energy storage is projected to grow to 1,000GW by 2040, up from just 9GW today (https://energy.mit.edu/research/future-of-energy-storage/). This exponential growth will be driven by continued declines in storage costs and the increasing deployment of renewable energy like wind and solar power that require storage to overcome intermittency.

On the economic front, lithium-ion batteries and other storage technologies are expected to continue getting cheaper. Costs for lithium-ion batteries have already dropped nearly 90% in the last decade and are projected to fall by at least another 50% by 2030 (https://sustainablefuturenews.com/features/the-future-of-energy-storage-batteries-and-beyond/). As storage gets more affordable it will increasingly be deployed to help balance grids, integrate more renewables, and provide backup power.

Conclusion

In conclusion, solar energy storage has both advantages and disadvantages that need to be weighed when deciding if it’s worthwhile for a particular situation. The main pros of solar storage are that it allows solar power to be used anytime, provides backup power during grid outages, and can reduce reliance on fossil fuels. However, solar storage systems are still quite expensive, have some environmental impacts from battery production and disposal, and may not provide a positive return on investment in some markets.

Overall, solar storage is most likely to be worthwhile for homes and businesses that already have solar panels installed, experience frequent power outages, have high electric rates or live in areas with incentives, and don’t mind paying more upfront to reap longer-term savings. As battery storage technology continues to improve and become more affordable, solar energy storage will make more financial sense for wider adoption. Each situation needs to be evaluated individually based on solar resource, energy consumption, grid electricity rates, incentives, and installation and maintenance costs to determine if the benefits outweigh the costs.