Can Green Gas Solve Renewable Energy's Intermittency Challenge?
Albert van der Molen faced a quandary. As Innovation Leader for Stedin, the third-largest grid operator in the Netherlands, his job is improving electricity and natural gas delivery while expanding the utility’s use of renewable energy. One answer was tempting – using excess renewable energy to create a greener substitute for natural gas while increasing capacity factors through energy storage.
He previously succeeded in turning power into hydrogen at a demonstration project, mixing it with natural gas in pipelines at up to 20% share. But hydrogen can’t completely replace natural gas delivered to customers, limiting its upside. “I asked myself which gas can we blend in with natural gas better than hydrogen, and the answer was simple,” said van der Molen, “The gas you can blend in best with natural gas is natural gas.”
That seems like a logical solution – once you add methanization to the equation. French scientist Paul Sabatier first produced methane from hydrogen in 1912 by adding carbon dioxide, and synthetic methane can be used by consumers in household appliances or for industrial processes under current Dutch regulations.
Since Holland features requisite resources like offshore wind and proximity to carbon-spewing industrial sites, whenever excess renewables are available, methanization could theoretically turn it into “green gas” with a similar energy content but lower emissions profile than natural gas – a concept Stedin termed Power2Gas.
After successfully producing methane in a laboratory setting, the path forward was clear to van der Molen. Now, he just had to prove it would work in the real world. “It is not rocket science – I like to call it Russian tractor technology,” said Van Der Molen. “But you have to do it, you have to prove that it’s possible.”
Blue Buildings, Green Gas
Stedin is one of Holland’s regional grid operators, serving customers primarily around Rotterdam and Utrecht. With 2 million electricity customers across nearly 28,000 miles of power lines and 1.9 million gas customers spanning 14,700 miles of pipeline, but one of the lowest annual outage rates in the world, the utility prioritizes service innovations.
So when van der Molen shared his idea with executives, Power2Gas started taking form near a 30-unit apartment complex in Rozenburg, a city located one hour outside Rotterdam. The demonstration system was built in one corner of a youth sports field, three small blue buildings surrounded by gleaming steel wire on a concrete pad, for around €1 million.
While the system won’t be fully operational until September 2014, it is now connected to Stedin’s existing electricity and gas network – making it the first residential power-to-gas project in Europe, according to spokesperson Harald Hanemaaijer.
A Simple Process Creates A Comprehensive Solution
Electricity and water flow into the hydrogen electrolyzer, housed by itself in one blue building, starting a chemical reaction that cleaves the water atoms into hydrogen and oxygen. The oxygen is released, and one cubic meter of hydrogen per hour flows from the building into the methanizer next door to be combined with carbon dioxide.
The hydrogen and carbon dioxide enter a series of four reactor vessels together and are then chemically divided in each chamber, increasing the methane percentage from 90% to 95% to 99% to 100% All tallied, Power2Gas will produce one cubic meter of green gas every four hours, or about 2,000 cubic meters annually while using 20,000 kilowatt-hours of renewables per year.
A few thousand cubic meters of gas may be a rounding error in the grand scheme of society’s energy needs, but two factors make the project fit perfectly onto Stedin’s system: First, the associated energy production is more than enough to meet the apartment building’s demand. If the apartment’s central heating system is running, the system will provide local heat to residents. If the heating system is off, gas will simply feed onto the grid.
That’s where the second factor comes into play. Under Dutch law, grid operators can’t produce significant amounts of natural gas. Power2Gas’s output is so small that it’s essentially offset by line losses across the system, keeping Stedin’s generation neutral.
And keep in mind, Power2Gas’s biggest success is proving the technology works, not becoming a major gas producer. By using currently available electrolyzers with larger capacity, the system could quadruple gas output, making it more attractive to larger customers or communities, according to van der Molen.
But Is It Actually Greener?
So all this begs the question – is Power2Gas’ green gas actually greener? The end product burns around 1% cleaner than natural gas, but because the process consumes equal parts carbon dioxide to produced methane, it creates a closed CO2 cycle. “It’s a way of ensuring we use the full potential of sustainable energy,” said van der Molen.
Power2Gas has other positive environmental aspects beyond emissions. Once the process reaches 500 degrees centigrade, its exothermic chemical reactions produce enough heat to self-perpetuate its internal chemical reactions. Water byproducts are also removed from the mixture during production, but they’re pure enough for release into the public drainage system.
If you think about Power2Gas, it could be another avenue toward the Holy Grail of renewable electricity – energy storage – of extra interest on Europe’s grid, where output from German renewables has surged, creating negative power prices from time to time.
But storing renewables as green gas could alleviate those concerns as renewables grow. “We all hope that there will be so much solar and wind that we reach the maximum amount of hydrogen,” said van der Molen.
From Small Output To Massive Potential
Beyond empowering grid operators to smooth out spikes in renewable energy production and meet peak demand, renewable energy producers could avoid curtailment by finding demand whenever their projects are generating electricity, while industrial users could profit by turning the system on when gas prices are high and electricity prices are low to optimize power costs.
Stedin sees a growth market among these customers, and has signed a letter of intent to deploy a second pilot project at an industrial facility. Once that pilot is proven, the utility plans to start marketing the system to suitable sites as a turnkey solution – potentially realizing the full potential of Power2Gas.
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