Written Evidence submitted by Ferry Harmer
Section: Page (s)
2 A diagram of the LHEC network. 4
3 Two turbine types and properties 5
4 An Appraisal of Professor Cebon’s ‘fig 3’ and my proposal 6-12 thereafter.
5 Appendices (Air Source Heat Pumps) 13-14
6 Renewable H2 scenario at 30% 15-17
7 References 18
A description of the problem and potential solution
I’m an Architectural technologist by education and an unashamed devotee to the most common element in the universe.
I happened to watch the oral session of evidence given on the 3rd of March 2021..
Professors Shah and Cebon were the subjects and I could not help but be puzzled as to why Prof’ Cebon was so negative toward the hydrogen network concept. I wrote to him and he very kindly sent me his blog link on the matter (*3).
Not having performed any levelled storage cost analysis I decided at first to take his word as gospel in terms of the overall efficiencies for the various types of energy storage methods. As you are aware Professor Cebon is a proponent for LAEC and says that it has managed to achieve a 68% overall efficiency.
The Claude and an updated Linde cycle liquifies the air and caverns store that liquid at -195°C and, at a given point in time, it is expanded. The cold caused by the expansion is absorbed by the cavern. Extra ‘waste heat’ from another process is used to heat the air above boiling point and thereafter drive a turbine creating 50hz electricity.
Professor Cebon’s version of a traditional H2 network model requires that a turbine powers an electrolyser (on land or sea) then that H2 is compressed for use later by fuel cells of various types. That model represents a 30% overall efficiency rating.
I can see Professor Cebon’s point of view why would we choose H2 given the glaring disparity?
Cost per MWh is obviously a significant part of this debate and even with the traditional H2-power-gas-power model I noticed that would give a rough MWh value of £26 (using an equivalent production and wholesale value of £50 MWh).
However, the LAEC efficiency 68% is not to be taken lightly and then last night it hit me.
Air is a compressed liquid gas, Hydrogen is a compressed liquid gas; why can’t we pump high pressure H2 through a vacuum sealed turbine too?
The friction co-efficient for H2 is much less than that of air because it is much less dense. However, given that H2 liquefies at an even lower temp (-252°C) right material choice for the turbine fan blades and powerful 150 Bar compression in the first place I wonder how much more electricity can be squeezed from the gas? Indeed, what if we used an H2 powered gas turbine as well or sent it to the fuel cell which would be most efficient?
Both LAEC and H2 or LHEC require compressors to squeeze the gases into caverns or tanks and so the costs associated with that are about equal.
Another issue to be resolved:
Are the massive copper cables used to transport the electricity to the electrolysers to costly and lose too much energy through cable resistance compared to FRP H2 pipes?
Indeed, it is possible to create H2 pressures of 1000Bar according to a paper published by a cryogenic conference held in Dresden during 2012 (*17)
So my assertion is that with some cold turbine research we could seriously improve upon the current 30% and more than double overall efficiency rating as described by Professor Cebon.
Not by competing with LAEC technology but by changing the gas in question and integrating it into the H2 network!
Mapping out the initial challenges:
A nuclear power plant generally has steam turbines that provide an overall efficiency rating of 33%.
H2 produces a typical flame temperature of 2040 °C when burnt in air. Therefore, a spike in MWh capacity follows from that realisation. Rolls Royce or Siemens would certainly know of suitable pipe materials and their cost per ton.
So in effect what we have done is produce a plant that can supply power to both gas and electric grids, increased efficiency by 100% and flexibility of use which also saves on overall cost. WE JUST NEED TO TEST. The technology already exists.
I’ve performed some very basic estimates in ascertaining the overall £ returns for a traditional H2 network over 30 years for a wind network that is wholly electrolysed and that amounted to around £20bn+ on top of the current peak demand revenues (See Appendices).
If we add the cold, jet/ gas and steam turbines to the network I wouldn’t be surprised if we added a further £20bn + to that original figure. The concept expands our ability to cope with peak demands while the fossil fuel plants are phased out and decreases our CO2 emissions by at least 98%. The cold and hot turbine combo could easily work in concert with the steel, cement, glass industries, manufacturing etc’.
An Appraisal of Professor Cebon’s ‘fig 3’ and my proposal thereafter.
I’ve since had a chance to read some of his reference documents and perform a few google scholar searches, ‘sciencedirect’ enquiries and even Wikipedia. I’ve seen a couple of papers on the liquefaction cooling techniques of both air and H2.
In prof’ Cebon’s blog diagram ‘Fig 3’ on page 7 he labels H2 liquefaction as being 90% efficient, which is very kind because it seems that is a relatively recent development.
Technologies for Large-Scale Electricity Storage
by David Cebon on 8th November 2020
Current 30% however, 90% H2 liquefaction efficiency proven to be possible:
“The CRBJT cycle minimizes the contribution of the less efficient isenthalpic (8–12 kW h kg−1) expansion and reduces energy consumption to 3.6–5.0 kWe h per kg of LH2. The demonstration of a small-scale (∼200 kg per day) hydrogen liquefaction plant based on the CRBJT cycle has indicated that an overall thermodynamic energy efficiency of 90% is possible.”
FUELS – HYDROGEN STORAGE | Liquid
L. Bonadio, in Encyclopedia of Electrochemical Power Sources, 2009
Thermal Management and Energy Efficiency (*5)
The same development was achieved for air liquefaction.
“When the isenthalpic expansion device is replaced by an isentropic expansion device, an increase in the exergy efficiency of about 60% is achievable for a compression pressure of 200 bar (Venkatarathnam, 2008). The liquid yield increases considerably and this cycle is known as the Solvay liquefier. This can be done by means of a turbine instead of the JT valve, using a two-phase expander or a cryogenic expander (Kanoğlu, 2001)” (*4)
Liquid Air Energy Storage (LAES) as a large-scale storage technology for renewable energy integration – A review of investigation studies and near perspectives of LAES
Cyrine, Damaka,Denis, et al, (2020)
What I still cannot get my head around is why the transmission losses through the electricity grid have not been taken into account on his Fig 3? Even though the resistance of copper is relatively low there is a cost in terms of wasted heat.
In one of Professor Cebon’s own reference documents: Does a Hydrogen Economy Make Sense? (Bossel, 2006), diagram fig 9 below clearly depicts a 10% loss in efficiency due to resistance caused by the grid itself, ‘AC via grid transmission (90%)’
Is the LAEC plant (which are quite large in spread) placed on a rig in the sea? Perhaps the air is pumped ship to shore first and then liquefied. Nonetheless I would like to know why it is not present on prof Cebon’s fig 3.
We have, for the moment, gathered that liquefaction is 90% efficient for both air and H2 due to developments in expansion valve technology and the like.
Where I get a little hazy in terms of my certainty is the true effectiveness of an LHEC method; it simply hasn’t been tried yet. So, all I can assume is that the 2nd law of thermodynamics holds true and that conditions tend to equalise out before the end.
Whatever happens I will assume similar overall efficiencies for both LAEC and LHFC processes of (70%), also that 90% AC grid losses and 90% liquefaction are also true. H2 is less dense and provides less friction but it’s volume and capability to be stored above 500 Bar (*17) mean that finding the appropriate pressure for that particular gas density will be possible. Thus, pushing round the turbine and providing cold power!
This is a quote regarding the LAEC process: Reported by the Institute of Mechanical engineers.
“In isolation the process is only 25% efficient, but this is increased to around 50% when used with a low-grade cold store, such as a large gravel bed, to capture the cold generated by evaporating the cryogen. The cold is re-used during the next refrigeration cycle.” The Institute for Mechanical engineers
Efficiency is further increased when used in conjunction with a power plant or other source of low-grade heat that would otherwise be lost to the atmosphere. Highview Power claims an AC to AC round-trip efficiency of 70%, by using an otherwise waste heat source at 115 °C. The IMechE (Institution of Mechanical Engineers) agrees that these estimates for a commercial-scale plant are realistic. However this number was not checked or confirmed by independent professional institutions.”
en.wikipedia.org/wiki/Cryogenic_energy_storage , 2021 (*14) and the BBC (*13)
There is surprisingly little available information on integrated air turbines. The heat for the air is also provided by the stators and friction for the rotors that rotate the shaft.
The comparison projection, given all the prior evidence is on p10, please note I have attached KWh for end use but not the £ Break even, because I do not know where Professor Cebon acquired that knowledge for LAEC. Consequently, I cannot predict break even cost for the integrated electrolyser, LHEC, hot turbine and Fuel cell networks. Needless to say, all that integration, flexibility for both the gas and electricity networks should save billions more over all. Especially if one takes into account the individual requirements for different geographies. That must save on infrastructure costs alone.
Fig 1: LAEC and the integrated LHEC network models
Summary of Projected Power Outputs from Fig 1:
Air Source Heat Pumps (250%) = 56/100*250=140, then (AC cable losses)
1.4 *90= 126 KWh heat for domestic use.
Electric Boilers (85%) = 56/100*85= 47.6, then (AC cable losses)
0.476 * 85 = 40.46 KWh heat for use.
Air Source Heat Pumps (250%) after 2 stage Gas Turbine generation = 70.5/100*250 = 176.25, then (AC cable losses)
1.7625*90 = 158.625 KWh heat for domestic use.
Electric Boilers (85%) after 2 stage Gas Turbine generation =
70.5/ 100*85 = 59.925, then (AC cable losses)
0.59925*90 = 53.9 KWh heat for use.
Air Source Heat Pumps (250%) after 2 stage Fuel Cell generation =
67.2/100*250 = 168, then (AC cable losses)
1.68*90 = 151.2 KWh for domestic use.
Electric Boilers (85%) after 2 stage Fuel Cell generation =
67.2/100*85 = 57.12 then (AC cable losses)
= 51 .41 KWh heat for use.
Understanding the Outcomes of Fig 1 :
LHEC is potentially more efficient than LAEC.
LHEC is potentially more flexible than LAEC because it creates both gas and electrical grid outputs.
LHEC network can also accommodate and integrate with the Carbon Capture and Storage (CCS) or Blue H2 method. So the increased bang for your buck works, you reduce CO2 with double the efficiency while Renewables like Wind and solar generation catches up with demand. Thus, no energy deficit risk for the entire UK! I also think that tech would work for the American Market.
Research needs to be done now to adapt and calibrate an LAEC system to deal with H2 for testing. Considering Bury and Sheffield are linked by the M62/M60 & M66; the logistics for transportation of H2 should be relatively quick and straight forward.
In essence, I do not believe both are competing technologies, both ITM and High-Power could collaborate to create something better that solves the looming energy crisis before it begins.
Air source heat pumps:
Like Ground source HP Air source heat pumps are relatively expensive to buy and install compared to gas boilers (*16). Also, without the availability of the Renewable Heat Incentive; the payback time would be greatly extended.
Recommended output (kW)
ASHP Purchase & Installation costs
£8000 to £16000
£7000 to £10000
£6000 to £8000
Copied from Tradesmenscost.co.uk, 2021 (*15)
The COP of 2.5-3 or 250% - 300% is brilliant, no one can argue there. However, there are practical problems when retrofitting to Victorian terraces and other relatively cramped (110m² or less) properties.
When fitting heat pumps, in the name of creating an airtight and thermally efficient building it is wise to insulate at the same time. Typically, that means £30K + insulating and at least £8k for the HP + labour costs in one go. This is without fitting any Mechanical Ventilation heat recovery system, which if one is pedantic about reducing KWh m²/ a they would also add that cost to the project as well.
This is in contrast to H2 boilers, in that, the old house already has an established service thermal bridge with the gas pipe coming from underground. One may fit the boiler first without disturbing the equilibrium of the property. This gives homeowners, tenants and landlords more time, less initial outlay and disturbance than performing all the necessary upgrades at once.
I’m not saying it’s impossible to fit Air source heat pumps to small properties but that if you do it first it can make the insulation stage that bit more awkward later. Awkward means cost and extra risk.
For instance, with HP one must drill through the wall, insulate and seal around the penetration for existing buildings. This can increase the risk of water ingress, thermal bridge and mould. As said on p12 one needs to either attach the air conditioner sized unit to the wall or leave it in the garden. Attaching steel brackets and bolts onto the brick wall again causes thermal bridges and requires special consideration to mitigate against.
“Traditionally, boiler systems have been sized to be plenty big enough so that they can raise the temperature of a building in a relatively short period of time. However, as discussed in the items above, low operating water temperatures are advantageous for heat pumps, so it is far better to operate a small heat pump for much longer hours with lower water temperatures. Furthermore, big heat pump installations are expensive to buy compared to boilers. All-in-all, this ‘steers’ us away from large-capacity heating systems using heat pumps.”
The condensing unit needs to be sited outdoors and takes up room in your garden. Admittedly, they aren’t large pieces of equipment, about the same size as a domestic air conditioning unit. However, if you have a small garden, like many new builds, it will take up a considerable percentage of your recreational space.
Backup in winter
Depending on the type of heat pump you have and where you live, you might need to use another heating method to keep temperatures at a comfortable level during a severe winter. However, winters in the UK are usually never too cold.”
Renewable H2 scenario at 30%
So for now let me present you with a numeric tale about a single 10MW wind turbine….
(Hrs in a year are: 24*365 = 8760 / 2 = 4380hrs.)
A 10 MW turbine is blown round for 50% of the year (4380hrs) producing 10MW*60seconds*60minutes*4380hrs= 157,680,000 MW per ½ annum.
For 8 hrs a day it is used for peak energy demand and for the rest of the day the stopped turbine is basically wasted potential energy.
24-8= 16 hrs, but let’s be kind; say 12 hrs a day is wasted potential.
157,680,000 MW / 2 = 78,840,000 MW unutilised potential energy. Thus, at 30% overall efficiency Green H2 transformation = 23,652,000MW created and saved for a cold yet still day.
10 * 60 * 60 = 36,000 MW produced in an hour = 10MWh. Wind cost as a mean figure given as $70 per MWh so $700 to produce. This price will vary because of site related variables etc’ but it is nowhere near nuclear’s cost per MWh of around $125 MWh.
78,840,000 MW / 36,000 MW = 2190 * 10MWh or 21,900 MWh.
The projection becomes a little tenuous from here on in because I’m using an out-of-date price per MWh (£35 https://www.businesselectricityprices.org.uk/retail-versus-wholesale-prices/). So let’s say £50 per MWh which is currently a tiny bit less than $70. Today’s £- $US valuation = £ 1 – 1.39
Naturally in future with electrolysers that cost falls quite dramatically because of the extra electricity sold to market.
£500* 2190 = £1,095,000 lost potential per turbine/ annum because there is no way to store it!
Even at 30% overall efficiency £1,095,000 / 100 * 30 = £328,500 per annum ( Remember: This scenario is as if the wholesale price never deviates from £50 while the cost per MWh production inevitably drops)
Includes the 50% lost due to H2 conversion back into electricity by fuel cell. Considering ITM’s projected costings of roughly £500k per MW capacity by 2023 means £5,000,000 per turbine. This projection doesn’t include future benefits of price reductions caused by increased PEM efficiency, other R&D and manufacturing LEAN production at scale.
Lifetime of a turbine: up to 30 yrs
£328, 500 * 30 = £9, 855, 000 unutilised electricity at wholesale prices created over the lifetime of the turbine: - £5,000,000 electrolyser costs = £4,855,000 extra revenues over the lifetime (exc’ inflation and any interest) per turbine.
Currently possess 24.1 GW of turbines in the UK (10,930 turbines) with roughly half their energy utilised. That number will expand to 50 GW by 2030
1GW = 1000MW
10MWh @ 30% Green H2 overall efficiency = £4,855,000 accrued over turbine life
100 * £4,855,000 = £485,500,00 accrued per GW of now utilised turbine energy over 30 years.
£485,500, 000* 50GW = extra £24,275,000,000 revenues over 30yrs.
This figure includes the installation costs of the electrolysers (£5,000,000 per 10MW) , excludes inflation, loan interest and, as far as I’m aware; excludes the required storage capacity cost for the gas. Nonetheless the revenue savings/ profits for this utilisation will probably be in the tens of billions.
Indeed, the inflation, H2 storage + extra CO2 storage costs and loan interest will be factors for CCS. CCS also has the 50% efficiency issue when it comes to converting blue H2 back into electricity via fuel cell technology.
Normal Peak demand projection; at 8 hrs a day per turbine/ annum: that is 2/3 the amount of MWh produced by 12hr projection. So 78,840,000MW / 3*2 = 52,560,000MW @ 100% utilisation/ 36000 = 14,600 MWh @ £50 = £730,000 per annum
21,900 MWh utilised @ 30% = 6570MWh
If 14,600 MWh = full yearly productivity and 100% of the £50 per MWh price tag.
How much does 6750MWh represent in equivalent percentage terms and denoted in cost reduction per Mwh?
14600/ 100 = 146 = 1%, so 6750 / 146 = 46.233% price reduction per MWh.
£50/ 100 * 46.233 = £23.11
50 – 23.11 =
Eventual Projected Wind: £26.89 per Mwh if every turbine had an electrolyser.
Furthermore, the staggered nature of the roll out, increasing efficiency of turbines, their manufacture, electrolysers and homes etc’ over the next 30 years have not been taken into account.
11. Does a Hydrogen Economy Make Sense? (Bossel, 2006)
(5 March 2021)