Solar battery efficiency. Solar and Battery Storage in Action at The Olde House, Cornwall

Solar PV and Battery Storage: the perfect mix for powering your energy efficiency and resilience

The sharp drop in costs of solar photovoltaic (PV) technology in the last couple of years is widely opening access to this technology, as evidenced by the prolific and increasing pipeline of projects seen worldwide. Customers of different sizes are improving their energy efficiency by self-consuming onsite solar PV generation, but the benefits of this clean energy are not fully exploited due to its temporal inflexibility, i.e. solar PV generated energy cannot be used when it is most valuable.

By combining Solar PV with Battery Storage to create hybrid renewable systems, organisations are benefiting from considerable and strong cost returns and unlocking new revenue opportunities, while improving their energy efficiency and resilience, and reducing their carbon footprint.

Falling costs and advancements in battery technology are increasing the affordability, durability and performance of battery storage. When co-located with solar, the commercial viability and wider benefits of both energy solutions are boosted.

Solar and batteries make a natural and effective energy mix. We examine the five key benefits of combining these technologies:

Improve energy resilience

You can protect your site against the increasing number of energy-related failures observed in the grid by instantly switching on your off-grid battery stored solar power in the event of any disruption in your energy supply. In a fraction of a second, you can gain access to a carbon-free power supply to keep critical processes and equipment operational, ensuring the continuity of your business, even during a prolonged energy outage.

Businesses should factor in the potential financial and wider business savings of solar battery energy resilience. The consequences of even the briefest power interruption in terms of damage to equipment, financial loss and inventory are serious. Our recent energy resilience report showed that 30% of our respondents had experienced energy disruptions which resulted in lost revenue. 23% reported equipment damage and 9% reported a drop in company value.

Solar battery solutions can also add another tier of emergency power for critical facilities, such as hospitals and data centres. In other instances, batteries may replace traditional back-up generators.

Increase the value of solar

Solar is a plentiful and green resource for generating renewable electricity during daytime. Our experience shows that by storing surplus solar generated electricity during this time and then using it flexibly and efficiently at times of low generation or peak demand, businesses can improve their financial performance NPV (net present value) from solar by an average 30-40% – sometimes even more.

This directly translates into increased sustainability and cost saving benefits from using more renewable energy and less expensive fossil-fuel energy. Consequently, it improves the return on investment of both the solar PV and battery, and can significantly increase the commercial viability of solar investment in the absence of subsidies and exposure to highly volatile wholesale energy markets.

Reduce energy costs

By using hybrid solar battery renewable systems, you can charge your battery at off-peak times and also at zero marginal cost when the sun is shining, to then utilise the stored energy at times when peak. This strategy can deliver huge cost savings, particularly if stored solar and cheap grid energy is used during red-Band DUoS and Triad periods. Centrica Business Solutions’ world leading forecasting capabilities enable us to accurately analyse and predict the highest cost periods to ensure that our customers can switch to battery power at the most opportune and valuable times.

The commercial case for solar battery hybrids is strengthened because of the potential to earn income via commercialising available storage flexibility. The ultra-fast response time of modern battery technologies makes them ideal for lucrative grid support services, such as dynamic Firm Frequency Response (dFFR), which requires a two-second response time. Our patented Virtual Power Plant technology can help you capture up to 52% more value from dynamic FFR.

In addition, businesses might benefit from the capacity market, which remunerates assets for being available to be dispatched at times of high system stress. There’s an additional opportunity to participate in the imbalance market, which serves the purpose of settling the imbalances between demand and supply.

The Basics of Solar Battery

All solar systems produce power at different times than homeowners use it. Solar systems will typically overproduce during the middle of the day compared to what the homeowner needs. Without battery storage, this extra production is back-fed to the utility grid through a program called net energy metering.

By selling their excess power to the grid, homeowners accumulate credit that can be used to offset the power they draw in at night when the solar panels aren’t producing power.

When a solar system is paired to a battery, homeowners have the option to use their extra electricity to charge up their battery instead of sending it back the grid.

When net metering is available, it’s not entirely necessary to pair solar with battery storage, however there are benefits to having both.

The Benefits of Pairing Solar With Battery Storage

So, why pay for a solar battery when the grid is there to credit you for your excess power anyway? As it turns out, there are several key advantages to pairing your solar system with battery storage.

Protection Against Power Outages

For most homeowners, the single biggest benefit of solar batteries is the ability to have backup power during a grid outage, including Planned Safety Power Shutoffs (PSPS).

If you have a solar system without battery storage and you experience a power outage, the solar system will automatically shut off. Electrical code requires that solar systems shut down during power outages so they don’t accidentally backfeed live power to the grid if the utility company has repair workers trying to fix the lines.

By contrast, with a solar and battery system, an additional device called a backup gateway is also installed that allows the house to “island”, or isolate, itself from the grid.

The moment the outage occurs, the gateway instantly detects the event, disconnects the home from the grid, and turns on the battery. The system then becomes a closed loop, where the battery powers the home’s backup circuits and the solar panels recharge the battery.

In this respect, solar batteries can function very similarly to home generators, except the time they can run for is a bit different. Solar batteries are far better in every measurable way. Check out our other article on the top ten reasons solar batteries are better than generators.

Time of Use Savings

Many utilities around the country are moving towards time of use (TOU) rate plans for their residential customers. These rate plans more accurately reflect the changes in wholesale power throughout the day.

Typically, these plans have peak charges during the late afternoon and early evening, when demand spikes as everyone goes home after the workday and increases their power consumption. The off-peak times are during the middle of the day, when solar systems everywhere are producing excess power, and overnight, when demand is lowest.

This difference in rates not only affects the cost of power that homeowners draw from the grid, but also the value of the excess power that homeowners backfeed to the grid.

This means that homeowners on time of use rate plans receive less credit for their extra power generated during the day than they pay for power they draw in during the evening. As a result, homeowners can owe money to the utility company at the end of the month even if their solar system met 100% of their power demand on a net basis.

This is where the additional savings from solar batteries comes in. Rather than backfeeding excess solar power when it’s less valuable, batteries allow homeowners to store their excess power on-site and feed that power into the house at night, which reduces the amount of power they need to draw from the grid during the highest-cost time of day.

The amount of additional savings that a solar battery will provide depends on several factors, including how much electricity the homeowner uses, what time of day they use that power, and the structure of their specific rate plan.

Self Consumption Energy Independence

Pairing their solar system with a battery also allows homeowners to use far more of their own clean energy.

Without a battery, homeowners will send a significant percentage of their solar power to the grid during the day, and then draw in dirty grid power at night.

To be clear, there are environmental impacts from mining and recycling the components of battery storage. However, they far outweigh the disastrous impacts of continued fossil fuel use.

With a battery, homeowners are able to produce, store, and use their own clean power around the clock. This not only provides the satisfaction of being more self-powered by clean energy, it also enables significantly more energy independence by reducing reliance on the grid.

Tesla found that adding just one of their batteries to a solar system increased the amount of solar energy consumed by the home by over 50%!

Solar and Battery Storage Incentives

Solar batteries may be eligible for both state and federal incentives, depending on the specifics of the installation.

The primary incentive currently available for batteries is the federal. which is now at 30% with the Inflation Reduction Act (IRA) signed into law.

That means you can claim 30% of your total solar and/or battery project cost as a tax credit. One of the new changes in the IRA is that battery storage no longer needs to be connected to solar in order to qualify for the tax credit. In other words, standalone battery storage and battery added to existing solar systems qualify for the new tax credit.

This state program offers an additional rebate for homeowners installing batteries who have particular backup needs. These include being located in Tier 2 and Tier 3 fire areas, needing backup for medical equipment, meeting low-income thresholds, etc.

There are also Bring Your Own Battery programs, in which utilities provide incentives for purchasing battery and connecting it to the grid.

Our Energy Advisors would be happy to assist any California homeowners looking for more information on the state’s SGIP program.

Between theory and reality: what you need to know

The calculations presented above allow for estimates in a perfect world. Unfortunately, we all know that reality is far more complex and that the subtleties of the real world tend to cause theory and practice to diverge.

Solar panels:

A solar panel is sensitive to several factors.

The main factor is the light intensity it receives. Fortunately, the sun shines (more or less) constantly, and the earth receives 1360 W/m² outside its atmosphere. But the light intensity that will reach the earth’s surface can be reduced considerably, and varies depending on

• The geographic location
• The season
• The time of day
• The orientation of the solar panel relative to the sun
• The weather (clouds, humidity)

The second secondary factor, but important nonetheless, is temperature. In fact, solar panels see their performance drop when the temperature increases. The temperature of the solar panel will depend:

• From the light intensity it receives
• From the temperature of the surrounding air
• From the wind
• Whether the solar panel is well ventilated at the back

Finally, certain characteristics of the solar panel will affect its power output:

• The cleanliness of the solar panel
• The choice of material covering the solar cell
• The age of the solar panel
• The quality of the cells and resistance to micro-cracking
• The internal ohmic losses during power harvesting and transmission.

Batteries

Batteries are less sensitive to their environment than solar panels. However, here are some important things to know about batteries:

Conversion losses

A portable external battery (powerbank) historically charges with a voltage of 5V to work with USB protocols (recently also with higher voltages such as 9V and 12V). However, the lithium cell requires a voltage around 3.7V. In order not to damage the lithium cell, it is necessary to convert the 5V voltage to 3.7V through a conversion circuit. When the battery discharges, this process is reversed, and the voltage must be increased from 3.7V to 5V in order to charge a portable device.

This conversion is unfortunately accompanied by losses, and some of the energy that was stored in the battery will be lost.

In addition, when the device charges from your portable external battery, it will itself have to bring the voltage down to recharge its own battery, which will create additional losses.

These losses depend on the quality of the control circuitry that is built into the product. An inexpensive product will often be susceptible to a less optimized circuit.

Speed of charge

The faster the battery discharges, the higher its output current will be. An increase in output current will also create higher internal losses, meaning there will be less energy left to transmit to your smartphone or other portable device. Having a battery that charges your devices more slowly therefore has an advantage in this sense.

How much capacity should my external battery have to charge my smartphone?

You can estimate the capacity that’s best for you by searching for the capacity of the battery that comes with your smartphone. A quick Google search will help you find this information.

Once you have found this information, determine how many times you want the battery to be able to charge your phone. You can then apply the following formula:

Desired capacity = capacity of your smartphone × number of recharges × 1.25

Example: An iPhoneX has a 2716mAh battery, and you want an external battery that can charge it at least 2 times. So the capacity you need is 2716 × 2 × 1.25 = 6790 mAh.

How many times will my external battery be able to charge my phone?

Inversely, you can also calculate how many times you can expect the battery to charge your device, by doing the reverse thinking.

number of recharges = Capacity of my external battery capacity of your smartphone × 1.25

Example: You want to purchase a Sunslice Gravity 20 portable external battery with a capacity of 20000 mAh. It will be able to charge an iPhoneX 20’000 / 2’716 / 1.25 = 5.89 times.

The importance of solar panel efficiency

One of the most talked about features in the solar panel world is energy efficiency. But what exactly is it?

The efficiency of a solar panel is defined as the power that a solar panel will be able to generate from the light power supplied to it:

Efficiency = electric power generated by the solar panel [W/m²] incident light power [W/m²]

Since this is a ratio of power fluxes and we are dividing Watts/m² by Watts/m², the efficiency has no unit. It is said to be dimensional.

We know that the incident light power is set by the environment, and thus varies between 1360W/m² (at high altitude, without clouds) and 0W/m² (at night). This variable is therefore beyond our control.

The efficiency of the solar panel will therefore determine the amount of electrical energy produced per square meter. A panel with a 20% efficiency will therefore require half the area to produce the same amount as a panel with a 10% efficiency.

The Role Of Battery Storage In Making Solar Energy Reliable

Battery storage plays an essential role in making solar energy more reliable. By storing excess energy generated by solar panels during times of high production, such as during sunny days, battery storage allows for the use of that energy during times when the sun is not shining, such as at night or on cloudy days. This helps to ensure a more consistent and reliable supply of energy, reducing the need for traditional backup power sources.

Additionally, battery storage also allows for the use of solar energy during power outages, providing a reliable source of emergency power. This is particularly important in remote or off-grid locations, where access to the grid may be limited or unreliable.

Another way that battery storage can help to make solar energy more reliable, is by providing the ability for utilities to store energy during periods of low demand and release it during periods of high demand. This helps to balance the supply and demand of energy on the grid and reduces the need for fossil fuel-based power plants to be used as a last resort.

The Impact Of Battery Storage On The Grid Integration Of Solar Power

Battery storage can have a significant impact on the grid integration of solar power. The ability to store excess energy generated by solar panels during times of high production and release it to the grid during times of low demand helps to balance the supply and demand of energy on the grid, which can reduce the need for expensive and polluting fossil fuel-based power plants to be used as a last resort.

Furthermore, by providing a reliable source of energy during power outages, battery storage can help to ensure a more stable and reliable power supply, reducing the need for expensive and polluting peaker plants.

Additionally, battery storage can also help to overcome the intermittency of solar power, which is one of the main challenges of integrating solar power into the grid. By storing excess energy generated by solar panels during the day, battery storage can ensure a consistent and reliable supply of energy even during times when the sun is not shining.

over, advanced battery management systems can be used to optimize the energy stored, and to manage the power flow to and from the grid, this allows for a better integration of solar energy into the grid, reducing the need for expensive and polluting fossil fuel-based power plants.

Latest Developments In Battery Technology

There have been several recent developments in battery technology. Some of the most notable include:

• Lithium-sulfur batteries: These batteries have a high energy density and a relatively long lifespan, making them well-suited for use in electric vehicles and other applications requiring high-energy storage. They also have a relatively low environmental impact.
• Solid-state batteries: These batteries use solid electrolytes instead of liquid ones, which can improve safety and increase energy density. They are also more durable and long-lasting than traditional lithium-ion batteries.
• Sodium-ion batteries: These batteries use sodium instead of lithium, which is more abundant and less expensive. They also have a relatively long lifespan and can be used in a wide range of applications.
• Silicon anodes: These anodes can increase the energy density of lithium-ion batteries, making them more efficient and longer-lasting.
• Flow batteries: These batteries use liquid electrolytes to store energy, and can be scaled up to very large sizes. They also have a relatively long lifespan and can be used for large-scale energy storage projects.
• Lithium-air batteries: These batteries have a very high energy density, making them well-suited for use in electric vehicles and other applications requiring high-energy storage.

In general, these developments aim to increase energy density, longevity, safety, and sustainability, making batteries more efficient and cost-effective, and open new possibilities for different applications. These new technologies are still in the research phase, and some of them are yet to be commercialized, but they have the potential to revolutionize the energy storage industry.

Why Are Batteries Important For Renewable Energy

Batteries Are Important For Renewable Energy For Several Reasons:

• Energy storage: Batteries are used to store excess energy generated by renewable energy sources, such as solar and wind power, for use during times when the sun is not shining or the wind is not blowing. This helps to ensure a more consistent and reliable supply of energy, reducing the need for traditional backup power sources.
• Grid integration: Batteries can help to overcome the intermittency of renewable energy sources, which is one of the main challenges of integrating renewable energy into the grid. By storing excess energy generated by renewable energy sources during times of high production, batteries can ensure a consistent and reliable supply of energy even during times when the renewable energy source is not producing.
• Cost-effectiveness: As the cost of batteries continues to decline, it is becoming more cost-effective to use batteries to store excess energy generated by renewable energy sources, which can help to reduce the overall cost of renewable energy systems.
• Energy independence: Batteries can provide a reliable source of emergency power during power outages, particularly in remote or off-grid locations, which can help to ensure energy independence and reduce the need for expensive and polluting fossil fuel-based power plants.
• Balancing the grid: Battery storage can also help to balance the supply and demand of energy on the grid, which can reduce the need for expensive and polluting fossil fuel-based power plants to be used as a last resort.