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Friday, December 22, 2017

Snowy Hydro 2.0 has competition

There are many ways to store renewable energy.

A problem with Snowy Hydro 2.0 is that it won't work without a large investment in additional 'poles and wires'. This is needed to move renewable energy to the centralised storage facility and to deliver it to consumers when needed. This very large outlay will add to already high electricity prices in Australia.

Another option reduces the need for spending on 'poles and wires' and cuts electricity prices: installing energy storage along-side solar PV systems owned by electricity consumers. See Affordable reliable electricity the easy way for a discussion on this option.

A different option for energy storage has even more advantages...

The Australian Government and other coal lobbyists express concerns with a fifty percent renewable energy target such as the one proposed by the Australian Labor Party:
"50% Renewable Energy by 2030 ...The Climate Change Authority has found that for Australia to achieve its bipartisan agreement to limit global warming by less than 2°C, renewable energy will need to comprise at least half of Australia’s electricity generation by 2030." 
Opponents make claims such as:
"Labor’s energy policy to deliver $200 bill shock ...Labor’s policy of a 50 per cent ­renewable energy target by 2030 would require the closure of 75 per cent of existing coal-fired power in Australia."
It's not as challenging a problem as some people think. Instead of using renewable energy to pump water uphill in a Snowy Hydro 2.0, it can be converted to despatchable fuel in two steps:
  1. Produce hydrogen by electrolysis of water.
  2. Use the hydrogen from the first step to manufacture methane from brown coal. 
The resulting fuel contains 50% renewable energy and 50% fossil fuel energy. If biomass was gasified in place of the coal, the fuel would be 100% renewable, despatchable energy.

The advantages include:
  • There is no need for fracking to produce coal seam gas.
  • There is no shortage of natural gas for the domestic market.
  • Inefficient old brown coal power stations that produce over 1,100 kilograms of carbon dioxide per megawatt-hour are replaced by efficient combined-cycle gas turbine power stations that produce only 330 kilograms of carbon dioxide per megawatt-hour. 
The reduction in carbon dioxide emissions from over 1,100 kilograms to just 330 kilograms per megawatt-hour points to a fairly remarkable benefit:
  • For Snowy Hydro 2.0 only about 2 megawatt-hours of renewable energy are returned for each 3 megawatt-hours of renewable energy that are stored... 
  • Carbon in brown coal is only being converted into electricity at an efficiency of about 25% in existing coal-fired power stations.
  • After this carbon is used to make methane with hydrogen from renewable energy, it is converted into electricity with an efficiency of 60% in combined cycle gas turbine power stations. 
  • This change means the amount of coal needed for the same amount of electricity is cut by over 70%. Output is increased, not reduced in this option.
E.on launches power-to-gas plant
E.on launches power-to-gas plant
The unit uses wind power to run electrolysis equipment that transforms water into hydrogen

The conversion of coal and biomass into high energy synthetic gases suitable for use as fuels focused attention on the hydrogasification reaction: C + 2H2 ⇄ CH4.

Because this reaction is highly exothermic and requires the presence of hydrogen, it has been suggested that it be integrated with endothermic hydrogen-producing reactions such as the steam/carbon gasification reaction, C + H20 ⇄ C0 + H2, and the methane/steam reforming reaction, CH4 + H20 ⇄ C0 + 3H2, to conserve heat and reduce the amount of hydrogen which must be provided.

It has been found that this can be done by reacting the coal or other carbonaceous material with steam and hydrogen in a hydrogasification zone to produce a methane-rich gas, passing at least a portion of this gas stream through a methane reforming zone where it is contacted with steam to reduce part of the methane and form hydrogen, and then recycling hydrogen and carbon monoxide recovered from the steam reformer overhead gas to the hydrogasification zone.

Coal char or other carbonaceous solids are circulated between the hydrogasification and reforming zones to provide heat integration.