Cities across the globe are striving to increase the portion of their energy that comes from renewable sources, such as wind, solar, and ocean tides. But these sources have shortcomings, as we noted last month
. "The problem with renewable energy is that sometimes the sun is not shining or the wind isn't blowing," said Ake Johnsen, marketing director for H-TEC Systems GmbH
At Hannover Messe
, April 8 to 12, 2013 in Hannover, Germany, Johnsen and colleagues will showcase solutions that specifically address this challenge. H-TEC is a subsidiary of GP JOULE, a German manufacturer of biomass power plants. GP JOULE launched H-TEC in 1997 to develop compact hydrogen generation systems.
It's important to realize that hydrogen is not truly a fuel "source." The reason is that it takes a tremendous amount of energy to separate the oxygen from the hydrogen in water molecules. Therefore, it's more like a form of chemical energy storage. That's how H-TEC sees it as well.
The company is developing hydrogen as a fuel storage system to bridge the gap between renewable energy capabilities and consumer needs. GP JOULE estimates that within the next few years renewable energy systems will have a generation capacity of up to 200 gigawatts (GW) on ideal days, while the average consumption is expected to be between 60 and 65 GW. (Currently, Germany has a cumulative installed solar panel power capacity
of 29.7 GW, and 27.2 GW capacity from wind).
Unfortunately, not all days will be ideal. "Whenever you have an excess of renewable energy, you can store that energy in the form of hydrogen," Johnsen explained. Then, on days when renewable sources are not producing enough energy, this power can be used as a supplement to reduce dependency on large power plants. It can also be used as emergency backup power in the case of a grid failure.
An electrolyzer device can store unused renewable energy into hydrogen for use later. Credit: H-TEC.
H-TEC's technology uses electrolyzers to convert water into hydrogen gas and oxygen. The process is the reverse of the one that takes place in hydrogen fuel cells. H-TEC's systems are comprised of several components -- an electrolysis unit, a water cooling and recirculation system, a voltage converter, and a controller for network connection. The electrolyzers are installed as a complete, plug-and-play unit.
When power is applied to the unit, water molecules are oxidized into oxygen, protons, and electrons. The protons are passed through a conductive membrane to a cathode, where they are introduced to the electrons and form hydrogen gas. Hydrogen is stored with a 75 percent efficiency rate. Waste heat is recaptured and recycled into local heating systems. The process requires no hazardous chemicals and produces no waste except for heat and oxygen (O2
One benefit of using hydrogen as a backup energy storage system is that the gas can be stored indefinitely without degradation. It can also be exported for a wide variety of applications. For example, it can be mixed in a 30:70 ration with natural gas or biogas from biomass plants. Alternatively, it can be used in fuel cells for cars, either funneled directly into the vehicle's tank or, more likely, a filling station. Johnsen believes this could be the big breakthrough that the car industry needs to push fuel cell vehicles into the mainstream.
Locally, the technology is an answer to another challenge. "In Germany, we have the issue that we are planning to switch off all of our nuclear power stations. Renewable energy needs to be available all the time," Johnsen said.