Backup power options: solar battery, diesel generator set and gas microturbine

A backup power supply is very important for buildings, especially during extended blackouts and other emergencies. Traditionally, backup power has been provided by diesel generators , but natural gas microturbines and solar-powered battery systems are also viable. As with any engineering decision, each option has advantages and limitations.

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Regardless of how your building is powered during emergencies, professional design ensures a reliable backup power system while meeting building codes. In this article, we will provide an overview of the three options mentioned above.

Solar battery systems

Solar energy is the fastest growing source of electricity in America , and the country's total installed capacity surpassed 100 gigawatts during the first few months of 2021. Solar panels become even more useful when combined with battery systems – your Electricity can be used at any time, not just when sunlight is available. Batteries can also be used for backup power, something that is not possible with solar panels alone.

One of the main advantages of a solar battery system is that it does not require any external fuel inputs, whereas diesel must be delivered by truck and natural gas must be provided as a utility. Additionally, backup generators powered by fossil fuels perform no function when the building operates normally, while a solar energy system constantly reduces your electricity bills.

The US offers a federal tax credit for solar power systems, currently set at 26% until the end of 2022. However, the tax credit also covers solar-powered battery systems as long as they meet the following condition:

• Residential battery systems: Getting 100% of their charge from solar panels.
• Enterprise Battery Systems: Getting at least 75% of your charge from solar panels.

A solar power system with batteries also operates with zero emissions, while diesel generators and gas microturbines release greenhouse gases when used. The adoption of solar energy is especially useful for New York buildings covered by Local Law 97 of 2019 – the law enforces emissions limits starting in 2024, penalizing building owners who exceed them.

Diesel Generators

Diesel generators have been field proven as backup power systems and have been tested for reliability in remote locations such as mines and oil fields. Diesel generators are also accepted by the vast majority of building codes, while battery systems and gas microturbines often face limitations.

• For example, stand-alone gas turbines are not accepted as emergency power systems in many building codes since they cannot store their fuel locally.
• On the other hand, a diesel generator can easily be equipped with a larger storage tank.

However, the reliability of diesel generator sets comes at a price. Generating electricity with diesel is very expensive – you can expect a cost of more than $0.30 per kilowatt-hour in most buildings, and more than $1.00 per kilowatt-hour in remote locations.

The use of diesel also poses a logistical challenge, as the fuel can only be delivered by truck. This can become a problem if transportation is disrupted during prolonged emergencies, such as extreme weather events. If diesel deliveries cannot reach a building, it will soon run out of backup power.

Natural Gas Microturbines

Unlike diesel, which arrives by truck, natural gas uses a network of underground pipes to reach buildings. As a result, the fuel supply for natural gas generators is much less likely to be interrupted and building owners don't have to worry about keeping the tank full and scheduling deliveries.

Natural gas produces emissions like any fossil fuel, but its CO2 emissions per BTU are lower than those of diesel by around 27%. Microturbines can also achieve a lower operating cost than diesel generator sets, making them a less polluting and cheaper source of backup power.

• Depending on local electricity rates and natural gas prices, there may be cases where using a microturbine as the main source of energy is more economical than using the grid.
• A gas microturbine can also be used as part of a combined heat and power (CHP) system, which provides electricity and heating.

However, gas microturbines also have their limitations. Assuming the same capacity, they are more expensive than diesel generators. Additionally, their use as emergency power systems may be limited by building codes that require on-site fuel storage.

Conclusion

Solar batteries, diesel generators and natural gas microturbines can provide backup power for buildings. However, understanding the pros and cons of each system is very important. Diesel generators are a tried-and-true option for meeting the emergency power requirements of most building codes, but gas microturbines and solar batteries can be used for purposes other than backup power.