Power-to-gas is an innovative energy storage system process using electrolysis, which produces renewable hydrogen as a byproduct. The hydrogen can then be blended with natural gas as a renewable percentage blend and injected into a natural gas grid.
“It’s the process of taking surplus electrical energy and converting it to hydrogen gas,” explained Cliff Crawford, hydrogen specialist with Enbridge Gas Inc., which is owned by Canadian-based energy company Enbridge Inc. “It makes the energy storage and distribution much easier.”
In hydrogen form, the energy can be stored for lengthy periods of time versus battery storage. Hydrogen also takes on additional usage beyond electricity needs, such as mobility and transportation. “It adds a lot of value,” Crawford said.
Enbridge is one of the leaders in this emerging technology. It opened the first utility-scale North American power-to-gas plant in Markham, Ontario, Canada, through a joint venture with Cummins Inc. (previously Hydrogenics). It was commissioned in 2018.
The plant recently completed a three-year contract with Canada’s Independent Electricity Systems Operator (IESO) for electrical grid balancing. IESO controls and trades all the power on Canada’s electrical grid. Adding renewable energy to the energy mix can stress the electrical grid, and Enbridge’s electrolysis process can help relieve that pressure by producing hydrogen for subsequent use.
Now, Enbridge Gas is exploring future grid opportunities. It is adding a compression and dispensing facility at the site, which will allow the company to take its surplus hydrogen and get it to end users. It will also investigate leveraging the hydrogen for transportation and other needs.
The plant currently offers 2.5 MW of energy storage but is expandable to 5 MW. It has a maximum theoretical hydrogen output of 1,080 kg/day.
Blending challenges
In 2021, Enbridge’s hydrogen-natural gas blending project began to serve the downstream market. It initially served power to 3,600 homes, which has now become 4,200 homes. “We’re blending 2% hydrogen by volume,” Crawford said. “That’s because we are regulated and 2% was the starting point that was deemed acceptable.”
He said that the project has eliminated 117 tons of carbon dioxide emissions annually for just those homes, showing the potential for larger-scale impact once the process becomes more widespread in the consumer market.
The project comes with challenges, however. Measurement capabilities top the list of challenges as they must measure both BTU heating value and confirmation of hydrogen concentration in the blended gas, and it has proved costly to maintain several analyzers and deploy training to support new devices.
In addition, analyzers must be able to accurately measure hydrogen concentrations in the range of 2% by volume flow within the blended gas stream. An upset in the process, such as excessive hydrogen gas concentration, could cause damage to a pipeline via corrosion of steel piping.
The are also commercial impacts. Gas customers are compensated to reduce BTU content by volume of 2% hydrogen blended gas. If blended gas is higher than 2%, the heating value drops and possible commercial impact and billing issues may occur.
Chromatography solution
Enbridge Gas turned to Emerson to help ease their concerns. Specifically, the Rosemount 770XA Gas Chromatograph technology can measure both BTU content and hydrogen within the gas stream.
“It was a two-in-one solution,” Crawford said.
Instead of using multiple analyzers, the Rosemount 770XA provides all the critical measurements needed to validate the blend composition. The result is the delivery of cleaner energy in a consistent and reliable manner.
The project’s success highlights the opportunity for energy companies to use clean hydrogen on a larger scale to achieve net zero goals with no major impact on infrastructure.
In addition, by using the Rosemount 770XA, Enbridge Gas has realized a cost reduction and reduced complexity.
Enbridge isn’t done expanding. A new blending project is in the works in Quebec, and the company is evaluating Rosemount gas chromatograph technology for blending up to 25% hydrogen by volume.
That means the possibility of even more cost and complexity savings for the company, and more emissions reductions for consumers.
