Mobile Heat - FAQs

Does it make sense from an energy perspective to move heat?

Yes.  Moving heat via thermal batteries on barges is highly energy efficient. 

Exact efficiency figures depend on the distance transported and the barge and tug configuration and propulsion.  For schemes studied to date the typical “energy cost” range is 1–5% of the energy moved.  The most energy efficient arrangement uses ingoing and outgoing tides to help move the barges. 

There is also an efficiency loss when storing heat in thermal batteries over time.  How much energy is lost depends on the cycling length (i.e. the frequency with which batteries are moved) and other factors, but it is typically 2%. 

Total energy losses are therefore typically 3–7%, or expressed another way, mobile heat via barge is 93–97% efficient for the modelled schemes, following capture of the waste heat.

Does it make sense from a carbon perspective to move heat?

Yes.  We plan to use either HVO (hydrotreated vegetable oil) or electricity to move the barges.  Electricity is the most efficient option, and its carbon content is steadily falling as the electricity grid decarbonises.  However, at the moment there are limitations on electric tugs including range and charging times, which can make HVO necessary.

For schemes modelled to date, the carbon cost of moving the heat is less than 1g/kWh.  For comparison, gas burned for heat has a carbon content of c.216g/kWh. (Both figures modelled on the UK Treasury Green Book).

Does capturing waste heat create carbon emissions?

Capturing waste heat that would otherwise go into the atmosphere does not create any carbon emissions, except to account for the small amount of electric pumping needed to circulate water through a heat exchanger.

If the waste heat is taken from a combined heat and power (CHP) cycle, there is a small loss of electricity generation, for a much larger gain in heat energy – typically in a ratio of 5:1 – 10:1.  At a system level this is represented as an increase in efficiency.  From a carbon perspective, to the extent that the “lost” electricity then needs to be generated elsewhere on the gird, a carbon content is assigned to that unit of electricity.  (This is the same approach used for calculating the carbon cost of heat pumps, except heat pumps typically have a lower ratio of electricity consumed to heat produced – meaning more carbon cost is assigned to them).  So, if 1kWh of electricity is lost to produce 7.5kWh of heat, then the carbon cost of that 7kWh of heat is the grid carbon content of 1kWh of electricity.  This is roughly a 90% carbon reduction using latest SAP figures, and due to fall further as the grid decarbonises with renewables.

Is this heat good value for money?

Yes, using waste heat is good value for money.  Exact costs depend on specific arrangements with suppliers of waste heat, consumers, and the volume and timing of required heat deliveries.  However, in almost all cases it is a lower cost decarbonisation option than the main alternatives: heat pumps, direct electric, or hydrogen. 

Are the thermal batteries safe?

Yes, the thermal batteries are safe.  

There have been well documented (but rare) instances of lithium-ion electric batteries combusting, but this is an entirely different technology.

Sunamp thermal batteries work by using phase change materials (PCM) that melt and freeze at a desired temperature. In the same way an ice cube holds a steady temperature of 0C in a drink, the SUnamp PCM holds its charged temperature for a steady release. Sunamp are world leaders in stable PCM chemistry, based on a long term partnership with the University of Edinburgh.

The PCM in Sunamp thermal batteries being used for mobile heat projects is non-toxic and non-flammable, being salt based.  It can be hot when charged (up to 120C) but this heat is within the battery casing, commercial grade insulation, and a shipping container, as well as being permanently mounted on a barge away from the public. 

Safe marine logistics is are also a key focus for our projects.  In London, our partner Cory has over 200 years of experience of safely moving barges on the Thames. 

Are thermal batteries long lasting?

The Sunamp thermal batteries are long lasting.  Sunamp’s core PCM has been tested to over 40,000 cycles, with a less than 5% decline in energy storage.  There are no moving parts.. 

Is this a secure source of heat?

By taking waste heat from existing activities in the UK, we reduce dependence on imports of gas for heating, and the demand on renewables. 

From an end user perspective, the delivery of heat is dependent on barge supply.  The waterways we propose to use are inherently resilient – they do not need to be closed for maintenance or repairs, and can handle significantly more traffic than currently use them.  In most cases, we would also expect large heat users to retain local heat generation capability as an emergency back-up.

Is the government supporting the scheme?

There are several central and regional schemes, designed to support the decarbonisation of heat. We are in discussion with central and local government about these. 

Are you looking at moving heat other than by barge, and outside the UK?

Yes.  Our leadership group have led global teams, and worked on major projects around the world.  We are starting with barges transport and the UK market, as an initial use case, with an intention to introduce other transport modes and markets.