Residential Green Hydrogen Generation & Storage
This is an on-going research project to look at the feasibility of using spare energy from our smart home solar installation project and wind energy, to safely generate and store hydrogen. I am also researching the technologies available to achieve this. The hydrogen generated and stored can then be used for heating, cooking or electricity generation.
As my energy analysis shows, we currently generate a lot more solar energy than we can use or store in our Tesla Powerwall or our CUPRA Born. Whilst I am also researching alternative battery technologies, generating and storing hydrogen provides the ability to store megawatt hours of energy. This scale of storage enables an 'energy buffer' to be created, protecting us from long spells of cold and overcast weather.
My preference is to have a closed 'black box' system, that sits somewhere outside of our home. Electrical energy will be stored or extracted and the rate will be controlled by my contextual smart home. This seems like a safer solution to me and avoids the need for pipework to a hydrogen gas hob. It will be simpler if we just use electricity for cooking, with electric ovens and an electric induction hob.
Context
The energy analysis for our current home shows that in the worst month of the year, we have historically used 528kWh of electricity and 3088kWh of gas for cooking and the heating our home. The most energy used in one day for heating is about 120kWh and the most electricity used in our home for everything else is about 16kWh (excluding EV charging).
I am assuming we replace the gas energy used for heating with an electrically powered heat pump with a COP of at least 3. On the coldest days we might therefore need 40kWh of electrical energy for heating and another 16kWh for the other things. This is assuming our next home is similar to our current home in terms of efficiency though. I practice, we plan to make it a lot more energy efficient and it will be 'super insulated'.
My assumption is that we would want to be able to store energy at a minimum rate of about 20kW and consume it at a maximum rate of about 5kW. Ideally, we would want to be able to store energy at a rate of 50kW or more, to ensure we capture all of the renewable energy produced.
Assuming a whole week of zero energy generation, we would need a useable storage capacity of 392kWh. Allowing for the system losses in a hydrogen generation and storage system, a figure of 1MWh would provide a nice safety margin.
On our current tariff we pay a standing charge of 35.86p per day for electricity and 25.56p per day for gas (these do not include VAT). This works out at £269.04 per year (including VAT) and these are costs that will be saved if we go off grid.
Hydrogen As A Fuel
Green hydrogen is the only type produced in a climate-neutral manner, using renewable energy. It's the only kind of hydrogen I'm interested in.
Grey hydrogen is the most common form and it is generated from natural gas or methane, through a process called 'steam reforming'. Hydrogen is labelled as blue when the carbon generated from steam reforming is captured and stored underground through industrial carbon capture and storage (CSS).
In electrical terms, the energy density of hydrogen is equal to 33.6kWh of usable energy per kg. To store 1mWh of energy would require us to store 29.8kg of hydrogen.
For comparison, diesel holds about 1214kWh per kg. 1kg of hydrogen used in a fuel cell contains approximately the same energy as a gallon of diesel.
Hydrogen Generation
T.B.C.
Hydrogen Fuel Cells
Hydrogen fuel cells produce no harmful emissions and when fuelled with pure hydrogen, the only by-products are heat and water. Hydrogen fuel cell technology is proven in tough conditions, including cold environments as low as -40°C.
The main downside of hydrogen fuel cells is that they are only about 40% to 60% efficient when converting hydrogen gas to electricity.
