Frequently Asked Questions

How efficient is a FAB?

Current 80% full system Round Trip Efficiency (RTE), for FAB larger than 1 MWh the aim is 84% RTE.

How much electricity (kWh) is stored in a typical system configuration?

The system in modular and is easily scaled for both power and duration:

Power delivered kW [MW] - from 1,000 kW [1 MW] to 100,000 kW [100 MW] and more, controlled by the number and size of turbo expander generators (multiple suppliers worldwide from 20kW to 50 MW).

Energy stored kWh [MWh] - from 1,000 kWh [1 MWh] to 1,000,000kWh [1,000 MWh] and more, controlled by the number of storage cylinders (volume) for longer duration add more cylinders (multiple suppliers worldwide).

If a client is consuming 1 MW per hour and requires a storage system to cover 6 hours use, a 6 MWh system is required (1 MW generator running on 6 hours of air).

How big is the system?

For every MWh the footprint  is:
2 x 40 ft ISO Container 

(or 1 x 40 ft ISO container footprint, double stacked, each container: w = 2.44 x h = 2.59m x I = 12.19m).

What pressure (bar) is it planned to store compressed air at?

Compressed natural gas industry standard 250 bar.

What is the expected cost for the above exemplary system?

Cost reduces with both increased power and duration.

Considering 6 MWh (1 MW continuous discharge for 6 hours) whole system capital cost is approximately £507 k/MWh considering storage element alone each additional MWh is approximately £240 k/MWh. 

What is the expected life of the system?

The solution has a 30 year plus operational life without end-of-life hazardous disposal, halving costs compared to lithium-ion.

How long can the system store energy?

Hours, days, weeks or months - the mass of air does not change unless it is generating electricity, the heat stores is fully insulated, with 300mm of insulation the heat loss from 180 degres Celsius water to the surrounds is 0.029 K/h. Therefore: 0.696 K/day, 4.872 K/week, 19.488 K over 4 weeks (worst case, without factoring in the reducing differential store temperature over time). Part of the inefficiency is expressed as excess heat, long term heat decay can be accommodated in system design.

How dependent is your solution on the availability of e.g. wind energy?

Any excess energy can be stored, from the grid or onsite it is an electricity in and our system.

How do you see competition from companies like Highview Power?

Highview Power (HP) are focused on long duration centralised energy storage while valuable to the National Grid Transmission Operator it is supporting a central generation pushing electricity to grid edge model. Sherwood is embedded storage at the grid edge working into the centre - there is space for both, a second distinguishing factor is round trip efficiency as HP are liquifying air it takes 3 to 4 compression and expansion phases, round trip efficiency, power in and out is low 42-50% (Sherwood Power 80%+).

Can the FAB system be expanded as we grow and need additional electricity?

The system is modular, additional generator power can be added by and additional run hours through the addition of more air cylinders.

If our lease runs out, can we take the system with us?

Yes, the FAB system is containerised, all modules can be moved to alternative locations.

Can you charge and discharge at different rates?

Yes, the system is asymmetric – it can be designed to charge and discharge at different rates and charge and discharge simultaneously

Are we able to vary the discharge rates or do we have to output at full capacity?

Yes it can be done, either by manipulating the power electronics or varying the discharge mass flow.