{"id":3212,"date":"2020-09-28T14:04:00","date_gmt":"2020-09-28T13:04:00","guid":{"rendered":"https:\/\/novacom.group\/csrf\/?post_type=blog&p=3212"},"modified":"2020-11-11T14:14:48","modified_gmt":"2020-11-11T14:14:48","slug":"hydrogen-for-heating","status":"publish","type":"blog","link":"https:\/\/novacom.group\/csrf\/blog\/hydrogen-for-heating\/","title":{"rendered":"Hydrogen for Heating?"},"content":{"rendered":"\n

The most frequently proposed ways to heat buildings in a low carbon future are using hydrogen <\/em>to power hot water boilers or electricity<\/em> to power heat pumps.  There are two low-carbon ways to make hydrogen: These are known as \u2018green\u2019 and \u2018blue\u2019.  This article compares the various options on the basis of energy efficiency, carbon emissions, infrastructure requirements and technology readiness.<\/p>\n\n\n\n

Key Take-Aways (TLDR)<\/h3>\n\n\n\n
  1. Heat pumps are far more efficient than Green Hydrogen for heating buildings.  The \u2018wind-to-heat\u2019 energy consumption of heat pumps is 1\/6 that of green hydrogen, for delivery of the same amount of heat. Therefore the energy generation costs for heat pumps are 1\/6 of those for Green Hydrogen.<\/li>
  2. As a consequence of the inefficiency of the Green Hydrogen route, it would require an inordinate amount of renewable electricity to heat the UK\u2019s buildings: approximately 40 times the current installed capacity of offshore wind.  The heat pump route would require significantly less additional renewable electricity.<\/li>
  3. In the UK in 2020, heating a building with an electric space heater creates about 20% lower carbon emissions than heating the same building with a natural gas boiler.  This percentage will improve with time as the electricity supply becomes cleaner (lower carbon).<\/li>
  4. Electric space heating will always generate about half the carbon emissions of Green Hydrogen boilers.  Electric space heaters are available off the shelf now and require no additional infrastructure.<\/li>
  5. The Blue Hydrogen route for heating buildings would require a 25% increase in the amount of natural gas imported into the UK, taking the imports to 60% of national consumption.  This would be detrimental to the balance of trade and energy security.<\/li>
  6. Neither the Green Hydrogen nor the Blue Hydrogen route is \u2018clean\u2019  Both generate substantial carbon emissions.  In 2020, the Green Hydrogen route emits 50% more carbon than burning natural gas in a condensing boiler.<\/li>
  7. Blue Hydrogen will always generate significant \u2018fugitive\u2019 CO2 emissions<\/a>, that escape into the atmosphere.  Consequently, use of Blue Hydrogen for heating would prevent the UK government from meeting its legal commitments for \u2018net zero\u2019 emission by 2050.<\/li>
  8. Heat pumps generate 1\/4 of the emissions of a natural gas boiler in 2020 and this will reduce significantly with time as the electricity grid becomes cleaner.  They are the most effective way to reduce carbon emissions from heating.  Heat pumps are available off-the-shelf, now.<\/li>
  9. It is unlikely that the infrastructure needed for Blue or Green Hydrogen could be built in time for 2040.<\/li>
  10. Government policy should promote the of use of heat pumps for heating new and retrofitted buildings and should reject Hydrogen as an option for heating.<\/li><\/ol>\n\n\n\n

    Green Hydrogen<\/h3>\n\n\n\n

    \u2018Green hydrogen\u2019 is created by passing renewable electricity through pure (distilled) water.  This splits the water into hydrogen and oxygen gases.  The hydrogen can be compressed and pumped through pipes to consumers and then burned in hydrogen-ready condensing boilers to heat buildings.<\/p>\n\n\n\n

    Energy Efficiencies<\/h4>\n\n\n\n

    The efficiencies of the main steps in the Green Hydrogen process are shown in the right path of figure 1. Multiplying these efficiencies together gives an overall end-to-end efficiency of 46%. The largest proportion of losses occurs in\u00a0the electrolysis step, which is\u00a0at best 75% efficient.\u00a0 The consequence is that\u00a0100kWh of renewable electricity would yield 46 kWh of heat in the building.<\/p>\n\n\n\n

    \"\"
    Figure 1.\u00a0 Heating buildings using electricity or hydrogen<\/figcaption><\/figure>\n\n\n\n

    The middle branch of figure 1 shows transmission of the electricity via the electricity grid to a consumer, where it powers a 95% efficient electric space heater (of the type you can purchase in a department store). This route would deliver 86kWh to the building: nearly 90% more heat than a Green Hydrogen boiler, for the same amount of renewable electricity.  A space heater can be plugged-into the existing electrical infrastructure.<\/p>\n\n\n\n

    The left hand branch of figure 1 shows use of grid electricity to power a heat pump.  The big advantage of this route is that the heat pump delivers 3-4 times more heat into the building than the electricity it uses.  (See a nice explanation of how this works<\/a> in \u2018Sustainable energy without hot air<\/a>\u2018 by the late David Mackay<\/a>).  Assuming a realistic \u2018Coefficient of Performance\u2019 (COP) of 3.0; the output of the heat pump route would be 270kWh of heat.<\/p>\n\n\n\n

    Conclusions: <\/strong>An electric space heater will deliver nearly 90% more heat per kWh of input electricity than a Green Hydrogen boiler.  A heat pump would deliver (270\/46) = 6 times (600%) more heat from the same amount of electricity as the Green Hydrogen route.<\/p>\n\n\n\n

    What are the implications of this factor of 6?<\/p>\n\n\n\n

    Firstly, the country would have to build six times the number of additional wind turbines or solar panels or nuclear power stations to generate the electricity in the Green Hydrogen case than for heat pumps. Consequently, consumers would have to pay 6 times the price for the energy to heat their homes. Alternatively, the government would have to subsidise the cost of hydrogen, which would have a permanently damaging effect on the economy.  There would also be very substantial environmental impact in building and operating the turbines.<\/p>\n\n\n\n

    Secondly, in2018, the UK used about 300 TWh of natural gas for \u2018domestic use\u2019 \u2013 mainly heating buildings [1]. (1 TWh is 1 billion kWh).  Making the crude assumption that the heating was done over 6 months of the year, the 300TWh would correspond to an average heating power of about 70GW.<\/p>\n\n\n\n

    If this 70GW of heat was supplied by heat pumps<\/strong>, it would require 70\/2.7 = 26 GW of additional renewable electricity. (For comparison the average electric power demand of GB<\/a> throughout 2019 was 31GW.)  This 26GW could be provided by offshore wind turbines, as follows:<\/p>\n\n\n\n