Hydrogen or a battery for your business? Hours to seasons

For hours and days, a battery is the better storage, and it earns money every day. For a whole season, hydrogen works in theory but loses about two thirds of your energy on the way. An off-grid system therefore covers the few dark weeks with a generator or the grid, not with a tank of hydrogen. The same logic applies on a grid-connected site with a business battery system.

Maybe you know the feeling. In June your roof produces more than the whole site can use. In January the same roof gives a fraction, and the battery is empty before the evening shift ends. Then someone says what many forums say: a battery is a stopgap for a few hours; hydrogen is the real battery, from summer into winter.

The idea is right about the problem and wrong about the fix, for almost every company. The hidden cost is not only the price of the machines. It is the energy you lose, the gas you must store safely and the years you wait while a battery could already save every day.

Our off-grid site at Special Renting in Zele, a rental company for lifting equipment, shows how big the gap really is. Solar power easily covers the demand for most of the year. Only in winter does the battery run short, and then the generator steps in. It covers about 5% of the yearly demand, with January as the worst month.

What is the difference between storing energy in a battery and in hydrogen?

A battery stores electricity directly; hydrogen turns it into a gas and back again. That extra detour is where the difference in cost and losses comes from.

In a lithium battery (LFP, lithium iron phosphate, the usual chemistry for stationary storage), electricity goes in and comes out through one inverter. There is nothing to burn and no gas to store. Our article on LFP, NMC and sodium-ion for a business explains the chemistry choice.

Hydrogen storage needs a chain of four machines. An electrolyser splits water into hydrogen and oxygen with electricity. A compressor pushes the gas into tanks, typically at 350 to 700 bar according to the US Department of Energy. A fuel cell turns the hydrogen back into electricity. And you still need a battery and inverter to deliver power at the right moment.

How much of your solar power comes back out of hydrogen and out of a battery?

About 92 kWh out of 100 from an LFP battery, and about 32 kWh at best from hydrogen. This figure, the round-trip efficiency, decides what storage really costs you.

Victron Energy gives a round-trip efficiency of 92% for its LFP batteries, against 80% for an average lead-acid battery. For hydrogen, each step loses a share. The US Department of Energy puts the best electrolysers of 2022 at 55 kWh of electricity per kilogram of hydrogen. One kilogram holds 120 MJ, or about 33.3 kWh.

Compression then costs 10 to 15% of the energy, according to WaterstofNet, the Belgian-Dutch hydrogen cluster. Fuel cells can exceed 60% efficiency, the Department of Energy writes. Multiply the steps and roughly a third of your solar power comes back as electricity.

The fuel cell does give off heat, which a site with a heat demand can use. But as electricity storage, every kWh you want back in winter costs you about three kWh of summer surplus.

Hours, days or seasons: which storage fits which gap?

Match the storage to the length of the gap. Most gaps on a business site last hours, some last days, and only a small share lasts a season.

Seen this way, the question is rarely "hydrogen or a battery". It is "which battery for the daily work, and which second source for the few dark weeks". Our article on how a generator and a battery share the work explains that combination on off-grid sites.

How big is the winter gap on a business site, and how much hydrogen would fill it?

Usually a few percent of the yearly demand, and filling it with hydrogen takes a lot of summer power and a lot of gas.

In Zele the generator covers about 5% of the demand. It starts for a couple of days from December, and January is the worst month. The rest of the year, the solar panels and the battery do the job on their own.

Take an illustrative site that uses 100,000 kWh a year, with the same 5% winter gap. To fill 5,000 kWh from hydrogen, you need:

• About 250 kg of hydrogen, with a fuel cell at 60% efficiency and 33.3 kWh in every kilogram.
• About 14,000 kWh of electricity for the electrolyser alone (250 kg at 55 kWh/kg), plus the compressor.
• A pressure tank that holds that gas for months, with the safety rules that come with it.

A battery sized to carry 5,000 kWh from summer to winter would cycle once a year. That is the most expensive way to use a battery. A battery pays when it cycles every day. That is why our off-grid battery designs size the battery on the daily need and leave the rare empty days to a second source.

Is hydrogen storage safe on a business site?

It can be made safe, but it is a flammable gas under high pressure, and that brings rules a battery room does not have.

The US Department of Energy lists the main points. Hydrogen ignites across a wide range of concentrations in air and needs less energy to ignite than natural gas. It burns with a nearly invisible flame, so special flame detectors are needed. Some metals become brittle in contact with it. On the positive side, it is very light and disperses fast outdoors.

In the EU, a workplace where an explosive atmosphere can form falls under the ATEX workplace directive (1999/92/EC). The employer must classify zones and keep an explosion protection document up to date. Add the environmental permit and the fire service. Ask both before you buy, not after.

A lithium battery has its own risks, and they are well understood. Our article on the safety, permits and insurance of a business battery covers them in detail.

What does hydrogen storage cost compared with a battery?

More per kWh you get back, for three reasons that do not depend on the price tag.

• Four machines instead of one. Electrolyser, compressor, tanks and fuel cell each need purchase, space, maintenance and inspection. You still need a battery and inverter next to them.
• Two thirds of the energy is lost. Every winter kWh costs about three summer kWh, so you also need more panels.
• Few cycles. Seasonal storage fills and empties once a year. A battery that shaves peaks and stores solar power works every day, so its cost spreads over many more kWh.

A battery earns its money in the daily work. It stores your solar power for the evening, cuts your quarter-hour peak and bridges a power cut. Our overview of battery storage for businesses shows what a battery does on a company site.

Can you make and store your own hydrogen? Technically yes, and small systems for homes have been sold. But they depend on a few suppliers, and the losses stay the same. For a company, we do not see that as a safe bet today.

When is a generator on HVO the better seasonal answer?

When the gap is a few percent of the year, a generator that is ready in minutes beats a seasonal store. HVO makes it cleaner.

HVO (hydrotreated vegetable oil) is a renewable diesel made from waste oils and fats. Its producer Neste states that switching needs no changes to engines or fuel infrastructure. It cuts greenhouse gas emissions over the life cycle by at least 50% compared with fossil diesel. Ask your generator manufacturer to confirm the approval for your model.

In Zele the generator runs only in the dark months and covers about 5% of the demand. On a farm in St-Georges-sur-Meuse, Wallonia, the site used to run on a generator day and night. Since solar panels and a battery were added, the generator is only the back-up.

A generator that waits for months has its own weak points: the starter battery and the fuel. Read why a back-up generator fails to start when you need it. Does your generator need a permit or inspection? See the rules for a back-up generator at a company.

Is there a grid connection? Then the grid can be your seasonal source. In a semi off-grid system the site runs on its own panels and battery, and the grid only charges the battery when it runs low.

Can wind or heat storage close the winter gap instead of hydrogen?

Often better than hydrogen, because both work in the season you need them.

Wind blows more in winter and at night, just when solar is weak. On a site in Beveren-Melsele that uses 350,000 kWh a year, we installed 200 solar panels and a 154 kWh battery. A medium-sized wind turbine will be added, and a high-voltage cabin supplies the missing peak current. Our article on a small wind turbine on a farm or business explains when wind pays.

Heat is the cheapest store for surplus. On a semi-off-grid site in Wingene, a boiler with a heating element takes over when the battery is full: water becomes the battery. There, the grid only acts as a back-up charger, and it can charge at market price on a windy winter night.

When does hydrogen make sense for a company?

When you use hydrogen itself, at industrial scale, and a pipeline or large supply is close by.

In Belgium, Fluxys is preparing a hydrogen network in and between the industrial clusters. That serves large users, such as chemistry and refineries, that need hydrogen as a raw material or fuel. An SME, a farm or a warehouse has a different need. A hydrogen store that only shifts electricity from summer to winter does not pay back its losses today.

What happens when you ask us to design storage for your site?

We start from your consumption over a full year, not from a technology.

1. Step 1: Measurement. We look at your consumption per quarter hour and per month, including December and January. If data is missing, we measure first.
2. Step 2: Design. Our engineering office calculates the panels, inverters, battery and, where needed, the generator: type and size for your site.
3. Step 3: Installation and commissioning of the full system, off-grid, semi-off-grid or on the grid.
4. Step 4: Monitoring. With our monitoring software you see in real time how much solar power you use directly and how much goes into the battery. You also see when the generator runs.

Our off-grid systems for companies and farms are always made to measure and can be expanded later, with extra panels or a wind turbine.