GB2447864A

GB2447864A - Phase change material energy saving device

Info

Publication number: GB2447864A
Application number: GB0701677A
Authority: GB
Inventors: James Anthony Smee
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-30
Filing date: 2007-01-30
Publication date: 2008-10-01
Also published as: GB0701677D0

Abstract

The invention comprises a system of heat storage modules using phase change materials (PCMs) which are removable from a source of heat and can be transported to a location where the heat can be used. Preferably, the beat storage modules are specifically adapted for use with cars, trucks, diesel railway locomotives, marine engines, industrial waste heat applications such as power and distribution transformers, marine offshore wave and wind energy generation, solar collectors and other naturally available energy sources. The system may also include storage bases and exchange systems as well as transport and reuse equipment. In use, the invention provides a complete system for the application of phase change materials to capture and store heat energy from the waste heat of mechanical and electrical equipment and then transport and reuse this energy at a location where the heat can be usefully discharged. Typically, heat from engines and transformers is stored in transportable modules using phase change materials and then moved and released as heating for buildings, homes and offices.

Description

Introduction. This invention concerns the application of Phase Change

Materials to capture and reuse heat energy from the waste heat of mechanical and electrical equipment Typically heat from engines and transformers is stored, moved and released as heating from buildings, homes and offices.

Basic Physics. When heat is removed or escapes from a hot liquid to a colder surrounding, the temperatui-e of the liquid falls. The amount of heat released per unit of weight per degree is known as the Specific Heat of the particular substance. When the liquid starts to change to a solid, heat is still removed or allowed to escape but the temperature remains constant at the temperatures of freezing or solidification, this heat is known as latent heat of fusion. It is defined in physics as the amount of heat liberated by one unit of weight of the substance. Thus for water the specific heat is I calorie per gram per degree centigrade, and the latent heat of fusion is 80 calories per gram. As much heat is stored at the phase change as is stored in raising the temperature by 80 C. The reverse is true when heat is added to a solid. The temperature will rise as heat is added, until it starts to melt or liquefy. At this point heat is added but the temperature remains at the melting point until all the solid is liquid, then the temperature of the liquid will rise as further heat is added. The heat stored at the melting point is the latent heat.

Different materials have different values of latent heat of fusion, and materials developed for use in storing energy at a particular temperature because of their high value of latent heat of fusion are known as phase change materials. Phase change materials which efficiently store heat at between say 50 C and 1 20 C can be used to give heat to room heating or to water heating systems. These substances are available commercially and used in heat storage devices. They are used to maintain a constant temperature whether hot or cold, they can absorb or liberate heat while the temperature stays constant. This is of course only within the capacity of the quantity of material used, when the PCM is fully solid or fully liquid then the temperature can change. Current applications are in cooler bags and hair curling rollers.

Practical Arrangement. A suitable container with PCM material is built into the design of an engine cooling system so that the PCM melts and heats up to around C. After some time, the container is removed and placed into equipment which will allow the stored heat to be used for space or water heating.

The PCM storage principle can be similarly applied to large distribution transformers, or any waste heat source. Typical arrangements are shown in fig I to fig 3. The description will describe the system for petrol and diesel engines.

Applications and Economics. Considering the internal combustion engines, petrol and diesel, the waste heat is roughly four times the mechanical output. That is about 20% of the fuel chemical energy is converted to mechanical energy and about 80% is lost as heat through the exhaust oil, radiator and engine block.

A typical 40 kW care engine is losing 160 kW in heat. A larger truck or bus engine maybe four times this and a locomotive ten or twenty times. A large ship may have a 2000 kW engine with 8000 kW of waste heat (8 MW) (I) Electrical energy is sold by the electricity companies at around 8p per kWhr, one kW for one hour costs typically 8p. So 1 MW for I week (168 hours) costs 1000 x 168 x 0.08 pounds i.e. 13,440 pounds. With other fuels such as gas or oil this could be about half, say 6700 pounds.

CARS. Statistics show 25 million cars on UK roads. Assuming cars are used on average for 10 hours per week or 520 hours per year, then if only 20% of the total lost heat (from line (I) could he stored and used, the available power, per year, would he: 25,000,000 x 32 x 520 = 416 billion kWhrs (2) If electrical energy is 8p per kWhr at present.

The value of the energy given in (2) is therefore 0.08 x 416 = 33.28 billion pounds.

TRAINS. A locomotive could carry a 1 ton storage container which could be changed at every station automatically as shown in fig 4. Then maybe 50% of the heat could be saved. For 2000 trains, running say 3000 hours per year, with 50% of 600 kW saved.

2000 x 3000 x 300 = 1,800,000,000 kWhrs. At 8p per kWhr this gives 144 million pounds.

BOATS. A large container ship storing heat is PCM stored in 40 ft containers at 25 ton each could value the 25 ton of PCM at over 200 pounds. If PCM could store heat at 100 calojies per gram, then at 4.2 joules per calorie, 25 tons would store 25,000,000 x 100 x 4.2 = 10,500,000,000 joules.

This is 2916 kWhrs or29 kW for 100 hours, enough for an office, school or shop for two weeks.

With careful design of a system more than half (50%) of the heat could be collected and reused, and engines are assumed water cooled under pressure. An air cooled engine can run at a much high temperature and so PCMs operating at 150 C or higher are feasible. Large collectors would be handled as goods, by fork lift truck and transport, small units installed in cars could be lifted out by hand and taken into the house to cool. An "empty" unit from the house would replace the one removed.

The container would he suitably insulated and adapted to he able to discharge all its stored heat by fans or pumps. The molten PCM could be sucked out or drained into another container but the solid material would need to be re-fitted to the heat source later. For private car use units or briefcase size, weighing about 25 kg, could be lifted out and taken into the house, perhaps two to a vehicle as shown in fig 2.

Vehicle such a buses, trains and ferry boats with frequent stops could swap containers at each stop and store most of the heat generated, using the normal water cooling radiator system only when the container became "fully charged".

The same principle of transportable heat storage can be applied to many other areas,

for example:

Power transformers generate "losses" as heat, of around 2-3%. A 1000 kVA transformer generates more than 10 kW of heat. With around 50, 000 transformers installed in the UK this means a total of 500,000 kW is available to be re-used. Over a period of one year this gives about 4 billion kWhrs of energy worth over 300 million pounds.

Waste heat from power stations, industrial processes, ovens and kilns, can all be arranged with heat transferred to PCM storage units for re-use. The exhaust from a gas turbine is over 500 C and many power plants now use the heat to generate steam for further generation and greater efficiency. Condensing steam from steam turbines is available at all coal and gas fired generation stations.

Novelty This application transports the heat as a saleable commodity, a quantity of heat is transported by hand, by fork lift truck, or other means to the place where it can be used. The novelty is in the fact that waste heat is not piped, pumped or transferred inside a building. It is stored in containers and physically moved to where it is needed. This invention is for a transportable heat bank adapted to efficiently take heat generated in one place and discharge it in a useful place.

Future vision Fully implemented nationally the system would have storage points in filling stations.

drive-in establishments, automatically operated roadside exchange units, motorway service areas, toll gates and so on. A driver would have indication when the unit was fully charged, then his vehicle would use it's normal water cooling system and he would start to look out for a depositing station.

So in theory a four hour car journey in a 100 hp car (75 kW waste), could store 1200 kWhrs of heat worth about 84 pounds of e1ectical energy, more than the present cost of the fuel. A large truck could be twice or three times this. Translated into coal or oil equivalent, or to carbon dioxide reduction targets, this could be an important contribution, with savings in billions of pounds each year.

Buildings around railway stations, motorway service areas, docks and ferry terminals would be built with this system in mind.

Calculations show that the total energy bill for the country could be halved by reusing energy in this way. This is a saving in oil, gas and electricity in the region of 250 billion pounds. The payback period would be perhaps 4 years in the overall cost was one trillion pounds, in fact the cost is only for the collecting and using infrastructure as transport and motorists would soon pay for their own conversions for the savings it would give them. With the possibility of more efficient phase change materials, the rising coal of fuels and energy, government assistance and carbon targets, and the possibility of vehicles and buildings designed to use a larger proportion of waste heat, this figure can only rise into trillions.

Claims

Claims 1. A system of heat storage modules using phase change materials

which are removable from the source of heat, and can be transported to a location where the heat can be used.
2. A system of heat storage modules using phase change materials which are removable from the source of heat, as claim I and are specifically adapted for use in cars and trucks together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.
3. A system of heat storage modules using phase change materials which are removable from the source of heat, as claim 1 and which are specifically adapted for use in diesel railway locomotives together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.
4. A system of heat energy storage modules using phase change materials which are removable from the source of heat, as claim I and which are specifically adapted for : use in marine engine applications together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be * used. ***. * ***

*
5. A system of heat energy storage modules using phase change materials which are * removable from the source of heat, as claim 1 and which are specifically adapted for * * *. use in industrial waste heat applications including large motors, power and * *** distribution transformers with storage bases and exchange systems, transport and reuse organisations where the heat can be used.

4. A system of heat storage modules using phase change materials which are removable from the source of heat, as claim 1 and which are specifically adapted for use in marine engine situations together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.

5. A system of heat storage modules using phase change materials which are removable from the source of heat, as claim 1 and which are specifically adapted for use in industrial waste heat applications including power and distribution transformers with storage bases and exchange systems, transport and reuse organisations where the heat can be used.

6. A system of heat storage modules using phase change materials which are removable from the source of heat, as claim 1 and are which are specifically adapted for use in marine offshore wave and wind energy generation, solar collectors and other naturally available energy sources together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.

Amendments to the Claims have been filed as follows 1. A system of heat energy storage modules using phase change materials which take heat from heat engines and machinery and are removable from the source of heat, and can be transported to a location where the heat can be used.

2. A system of heat energy storage modules using phase change materials which are removable from the source of heat, as claim 1 and are specifically adapted for use in cars and trucks together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.

3. A system of heat energy storage modules using phase change materials which are removable from the source of heat, as claim I and which are specifically adapted for use in diesel railway locomotives together with storage bases and exchange systems, transport and reuse equipment & organisations where the heat can be used.