This breakdown uses estimate inputs and assumptions to calculate its outcomes. Assumptions and inputs are described through the evaluation and workings. Another assumption is that the site energy consumption has stayed the same as when the site was running on HVO. If the site energy consumption has changed, then the case study does not show this.
We would also be able to give a clearer calculation if we knew the exact capacity of the solar racks shown in the case study. This capacity has been estimated using what we expect to be seen as optimistic numbers.
An ultimate evaluation and comparison between diesel could be given if the site energy consumption and power requirements were known.
Main issue observed
An initial read of the case study indicated either a discrepancy in energy requirements, appropriate sizing of equipment, or an unrealistic view on hydrogen costs.
On this basis a number of things could be happening behind this case study:
Diesel consumption has been overstated (pushing the diesel cost up) Hydrogen has been understated or seasonality not accounted for (pushing the hydrogen cost down) There is an unrealistic view on the amount of energy solar can provide (and more hydrogen will be needed, increasing cost) The cost of hydrogen is impossibly low (keeping the cost down) Diesel generator is still far too large and running extremely inefficiently (driving up fuel use, and fuel costs). From a deeper review of this study it seems this is the perfect example the inadequacies of diesel generators vs a modern hydrogen fuel cell hybrid setup. Namely that diesel generators will always have to sized in order to meet the peak power requirements. But that peak load will be infrequent, short and many times the size of the normal operating power requirement. Often the generator will be running at 10% it’s rated power, leading to drastically lower energy efficiencies*. In turn commonly leading to 3x the fuel consumption than the estimated consumption at project initiation. In other words, the costs presented up-front for diesel generators are often just theoretical, based on impossible assumptions around operating a generator at the most efficient load.
In this case most likely the equipment used, both the diesel generator and they hybrid setup, were correctly sized for the power and energy needs according to what each technology can provide. In this case it meant that a 60kVA generator was needed to cover peaks, but under the majority of normal conditions it would have been running very inefficiently. For the energy from diesel consumption to match the energy from on site solar+hydrogen the generator would have been running at around % efficiency.
This is a great case study in showing how we need to move to modern setups, and that doing so can deliver better site power while achieving cost savings against the real costs of the typical diesel generator setup.
Analysis methods summary
There are a few ways that this case study and the numbers can be evaluated:
Looking at the energy that would be provided by the diesel generator as the baseline energy requirement. Then looking at what energy would be provided by solar and hydrogen. Look at the hydrogen refuelling timings and the energy this would provide, comparing that to the energy provided by diesel. Evaluate the amount of energy/loading profile that could be supplied by a 44kWh battery and 4kW fuel cell.
*example energy efficiency curves for diesel generators. At 10% load you can be as low as 5% fuel efficient
Method 1 - reviewing energy from diesel and solar
Energy from HVO diesel? How much energy is coming from the diesel?
If the site is using litres per year this will correspond to : kWh per year of energy use by the site. This already assumes that the generator is operating at a not great total energy efficiency of % which would correspond to an operating load of around 50%. Already starting from a point of an oversized generator possibly.
Energy from solar? How much of the site consumption does the solar system deliver?
The solar system provides % of the site’s annual consumption, based on evaluating energy that would have been provided by the HVO diesel generator. The rest of this energy must come from elsewhere.
How much extra energy needs to be accounted for?
An extra % of the site’s energy consumption (based on the diesel use) must be provided by hydrogen. Of the total site consumption of kWh per year, there is a missing energy deficit of kWh. In this scenario, this kWh missing energy needs to be supplied by hydrogen.
Cost of hydrogen - is the stated charge for hydrogen fuel realistic?
The study suggests a cost of hydrogen per kg of circa If the missing energy is all supplied by hydrogen, this would mean the case study is paying per kWh of hydrogen fuel. This cost is based on the stated cost of hydrogen supply as shown in the case study ( per annum).
How expensive is hydrogen really?
Quoted prices for a much higher scale of hydrogen deployment are at circa £/kg. Usually, for the type of deployment pictured in the case study, costs per kg hydrogen would be closer to £70/kg in 2022.
Even if we take £26/kg as an optimistic cost for the case study’s hydrogen, and we assume that the stated diesel requirement was correct with respect to the energy needed on site, this would put the total cost for the hydrogen deployment at:
New annual cost for hydrogen fuel if energy of diesel is needed: Total deployment annual cost with increased hydrogen fuel use at optimistic market prices:
This just shows that if all of that diesel were turned into energy and was needed by site - then the real cost of hydrogen would be much higher. So either there is too much diesel being burnt, or not enough hydrogen.
Method 2 - reviewing the stated hydrogen volumes
Amount of hydrogen consumed as indicated by case study
Hydrogen volumes hard to say. If they were having bi weekly deliveries as stated for 2x MCP packs every 2 weeks, or 1 pack per week. This would have meant consuming kg hydrogen over the year.
Cost of the hydrogen
However, the stated costs for the implied hydrogen use in the case study is inline with BOC market rates. Based on the cost and the hydrogen volumes stated in the case study, hydrogen will be costing around /kg. Which is inline with the BOC costing Hydrologiq receives. Using hydrogen fuel pricing for fuel Hydrologiq was supplied by BOC during summer 2022, the total cost of this hydrogen would be around for the year with no additional servicing cost added.
Amount of energy from hydrogen vs stated from diesel
However, the indicated amount of hydrogen fuel only gives a yearly total usable energy from hydrogen of kWh. This is kWh less than would come from the supposedly correctly sized diesel generator and reduced diesel consumption. This energy deficit have to be made up by the solar and battery storage. This would equate to a daily energy requirement from the solar of kWh. The analysis of the solar system in Method 1 showed a lower output is likely from the deployed system in that location.
Method 3 - evaluation of the potential from the equipment
Loads capable of being served by the deployed hydrogen + battery setup
Assuming that the load on average had a 8kW baseload for 8hrs, with an aggregate of 10 minutes of peak draw at 18kW, a 44kWh battery and a 4kW hydrogen generator would be needed to cope with the demand when the sun wasn’t shining. This was approximately the size of the system that was installed. To go beyond these loads, the required setup wouldn’t cope.
Energy output from the setup
This loading would give a total daily energy provided to the site of 68kW, or 338kWh assuming 5 days running, or 473kWh assuming 7 days running.
Energy output from the diesel setup
However, the diesel consumption numbers would indicate that the 60kVA would have provided the site with kWh/day.
There is a large difference in what energy output the battery + hydrogen setup can provide and the energy being provided by the diesel fuel (even after efficiency conversions).