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Customer application 28 August 2020
Power-to-Gas: A Beacon of Hope for the Smart Grid

Power-to-gas systems, which convert excess electricity into storable hydrogen and methane gases, could play a decisive role in the future of the energy market. After all, the systems couple the power sector with heating and mobility, and thus incorporate two important areas of climate change mitigation. WAGO’s controllers facilitate connection and communicative networking of the systems into flexibly controllable virtual power plants.

Climate change mitigation has been given a high level of priority in Germany. By 2050, the proportion of electrical consumption from renewables is to be increased from a current value of 35 % to 100 %. Experts consider a higher rate of expansion quite likely, because, in their opinion, if climate change is actually to be limited to 1.5 degrees Celsius, then renewable energy sources must also fully supply the mobility and heating sectors by 2050. However, the power lines are already stretched to the limit, due to the fast expansion of solar and wind energy. Renewable energy production is subject to weather-induced fluctuations and must be adapted to demand in order to maintain network stability.

From Electricity to Gas – and Back to Electricity Here’s How WAGO Supports You:

  • Easy connection of power-to-gas systems at the control level using the WAGO Telecontrol Gateway WTG
  • Trouble-free integration into virtual power plants using the new VHPready communication standard
  • Encrypted data transmission via OpenVPN or IPSec

Integrated Energy: Electricity, Heat and Mobility

Storage devices can solve the problem by accommodating excess current and discharging it as needed. While battery storage devices are suited for drawing excess electricity quickly from the network in the short term, so-called power-to-gas systems can provide long-term storage to relieve strain on the grid. The technology is currently being tested in a number of projects. Whenever wind farms produce too much electricity for their surroundings, the excess power is converted to hydrogen using electrolysis. The gas is stored in tanks, and the heat generated through electrolysis is supplied into the district heating network. When electrical consumption rises again, the hydrogen is burned, for example, in a connected biogas system.

Electrolysis as a Key Technology

This technology could play an important role, because hydrogen could be used beyond the energy sector. It could also be supplied as a raw material to the chemical industry, or as fuel for fuel cell vehicles. Or it can be converted into methane and provided to the existing natural gas network that supplies district heat, power plants and natural gas stations. However, some technical problems must be solved before power-to-gas is ready for market. The systems must be able to react to constant load changes due to the volatile nature of renewable energy production. New types of PEM electrolyzers (polymer electrolyte membranes) could enable this and quickly follow fluctuations. In the PEM method, distilled water is used as an electrolyte, which is electrically split into hydrogen and oxygen in milliseconds using a specialized, proton-conducting membrane.

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Fuel cells produce emission-free electricity from the hydrogen that was produced through electrolysis by the power-to-gas systems. However, the technology needs to be optimized further.

Technical Innovations Develop Quickly

For large scale use, the converters would have to be both more compact and more durable. Another flaw lies in their efficiency. Electrolysis converts electricity into hydrogen at a maximum efficiency of 80 %. Adding methanation reduces this to 50 %. If electricity is generated again at the end, the efficiency drops to less than 40 %. In addition, methanation only works from carbon dioxide (CO2) that is converted, by the addition of hydrogen, into methane and water. However, where should the CO2 come from in the future? It has been suggested that the gas could be filtered from air directly on site using adsorption systems; however, this method is not nearly market-ready. In spite of the hurdles, experts believe a breakthrough is coming in power-to-gas, because essential technical advances are on the horizon. In addition, the efficiency of the systems can be increased through skillfully configuration. If the waste heat from the electrolysis and the methanation is used as district heat, then this increases efficiency.

Natural Gas Network as Long-Term Storage

Many companies are testing the technology in numerous projects in order to bring power-to-gas online. Among other things, they are testing how much hydrogen can be stored in the natural gas network. Currently, the proportion of hydrogen cannot exceed five percent due to the high energy density. However, could the safe technical limit be higher? If so, then the natural gas network could be used more intensively as long-term storage. Another way to use hydrogen is by converting it into hydrocarbon, which is a fuel. Following electrolysis, part of the hydrogen is reduced to carbon monoxide (CO2). This is then mixed with the remaining hydrogen and forms the basis for a method in which a highly purified fuel is generated, which could replace diesel.

Compatible Solutions Are Needed

WAGO can help to link power-to-gas into the smart grid and into flexibly controllable aggregates, so-called virtual power plants. The electrical, gas, heat, and water supply systems are becoming more complex due to the increasing number of decentralized systems. This can lead to a confusing network with different interfaces from different manufacturers. Intelligent, flexible telecontrol solutions, which can meet users’ need for compatible solutions, are thus more necessary than ever. The WAGO Telecontrol Gateway (WTG) offers a solution. Using the WTG, up to 16 telecontrol substations can be linked in an open structure at the control level. This provides suppliers with a new degree of freedom, transparency and cost-efficiency. WAGO’s WTG introduces, for the first time, an open transmission level between participants both in the field and on the control level. A PFC200 Controller with WAGO Telecontrol Software as a communication gateway connects the telecontrol substation to the control level. The WTG can be used anywhere that substations are to be connected, independent of the manufacturer.

Easy Communication via VHPready

Another problem when combining decentralized systems, like power-to-gas, is that they do not even speak the same language, due to different manufacturers, and they are thus difficult to coordinate. WAGO can ensure better communication: WAGO’s telecontrollers meet the requirements of the VHPready (Virtual Heat and Power) communication standard and thus ensure trouble-free connection of systems in virtual power plants. The current version of the specification is VHPready 4.0. It combines control and communication within the virtual power plant and functions as a virtual interpreter to ensure that control centers and systems understand each other. VHPready standardizes the objects and variables of different communication protocols and explicitly declares them. Instead of a system-specific set of variables, as was previously the case, VHPready communicates via predefined profiles using explicitly defined data point lists. In addition to communication, domain-specific specifications, e.g., concerning behavior and reaction times, are also defined. This provides the ability to control systems using timetables. Thus, the control center can transmit control parameters to a system for a time period of 24 hours as a command/set/message/file. Data security plays a central role. The WAGO Controller can directly establish a VPN tunnel via OpenVPN or IPsec in order to transmit encrypted data to and receive it from the control center. The technology for integrating power-to-gas into smart grids is already available.

Text: Daniel Wiese, WAGO

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