GB2457139A

GB2457139A - Water heating system comprising an immersion heater supplied with electricity generated by an alternative energy source

Info

Publication number: GB2457139A
Application number: GB0802459A
Authority: GB
Inventors: Nicholas Julian Jan Francis Macphail
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-02-11
Filing date: 2008-02-11
Publication date: 2009-08-12
Also published as: GB0802459D0

Abstract

A water heating system comprises a thermal storage boiler or a thermal storage combination boiler, where the boiler's thermal store 1 acts as a heat source and thermal reservoir for providing heated water to a heating system and/or to provide domestic hot water. Preferably, the thermal store comprises at least one mains powered immersion heater or boiler. The thermal store may also incorporate other heat sources such as a heat pump, a combined heat and power (CHP) unit, or solar panels. One or more immersion heaters 2, 3 are provided within the thermal store, or within a hydraulic circuit connected to the thermal store, which are supplied with electricity by a micro generation alternative energy source. Preferably, the alternative energy source includes a wind turbine 4 and/or a photovoltaic (PV) array 5.

Description

THIS INVENTION RELATES TO IMPROVEMENTS IN THE UTILIZATION OF

INTERMITANTLY GENERATED ELECTRICITy It has become common practice with gas and oil fired boilers to use a thermal store together with a plate heat exchanger as shown in patent No 2266762 to provide wet system central heating and/or mains fed domestic hot water. This arrangement has advantages over non storage arrangements, for example gas fired non storage combi boilers, in that a far greater short term flow rate of hot water to taps is achievable from a storage combi for a given instantaneous boiler load. More recent types have enabled off peak electricity to be utilised as, with a somewhat larger thermal store, the thermal mass of the store enables the production of heating and hot water to continue through the off part of the off peak cycle.

With the increasing importance of the use "alternatives" to burning carbon-based fuels electricity, perhaps surprisingly given the comparative inefficiencies of its generation and distribution, becomes a sensible alternative to local burning of carbon-based fuels for heating and domestic hot water. These advantages stand out when electricity is used for heating and hot water supply with a thermal storage device, as the thermal store allows the input of heat energy to be suspended at times of peak demand while the thermal store's output to provide space heating and hot water can continue.

The storage combi is attractive to the generating companies because most of the alternatives to burning carbon-based fuels for electricity generation (for example nuclear, wind, and tidal generation) cannot be switched on or off instantly to suit demand. Although remarkably useful to meet base loads, "alternatives" have not been favoured by the generating companies as they cannot meet unexpected (or indeed expected) peak load demand.

Electric thermal storage devices, like electric thermal storage combis, that can have their loads remotely switched off by the generating companies' during times of peak load provide a good means of providing a predictable base load while offering the option of peak load shedding needed by the generating companies to make best use of the "alternatives".

Electricity generating companies are able to sell greater amounts of electricity without any need for greater generating plant as greater use is made of existing capacity. Electric storage combis are thus attractive financially to the generating companies and have attracted special low cost charge rates to encourage their use. These lower charge rates, in turn, make electricity more attractive than burning carbon-based fuels and will help with the reduction of carbon emissions required in the Kyoto and similar agreements and will reduce our * ::* dependence on fuels from sometimes less than co-operative countries. **SS

Thermal storage boilers/combis will help (indeed are helping) to reduce the use of the finite carbon-based fuels used in the supply of domestic heating and hot water.

* It has become increasingly important in the struggle to reduce our production of C02 to * utilise alternatives to the combustion of carbon based fuels. Micro generation of electricity by, for example, wind generators or photovoltajc arrays are beginning to become economic * enough for them to be considered for household use. The intermittent output of such micro generation is commonly sold back to the local electrical generating company. S.... * .

Problems exist with this arrangement, however, as, in addition to the micro generator's purchase and installation cost, there is a substantial additional cost of the complicated electronic controls needed to convert the generator'/s' output to a form that is suitable for t inputting to the mains supply. Further there is also a substantial cost of metering and accounting the supply to the mains that has to be bourn by the generating company and/or the householder.

Micro generation is difficuit to utilise in other ways without thermal storage because the output is Unpredictable and intermittent. It is impracticable for electricity to be stored except in a limited way in expensive batteries It is the aim of the present invention to improve on or obviate the above-mentioned problems.

According to the present invention there is provided a thermal storage boiler or thermal storage combi boiler system. The boiler's thermal store acts as a heat source and thermal reservoir of priinaiy water for providing heated water to a heating system and/or a heat exchanger to provide mains fed domestic hot water. Within the thermal store is provided, in addition to or instead of input from a conventional heat source (for example gas or oil fired boiler or mains electrically powered immersion heaters), immersion heater/s specifically to accept the intermittent output from electrical generation by, for example wind generator/s and/or photovoltajc array/s.

In a preferred form off-peak electricity is used as the primary heating means for the thermal store with the micro generated electricity, being of unpredictable and intermittent nature, used as a supplemental heat source to the thermal store. Much cost is saved by being able to eliminate the complicated electronics; metering and accounting needed by mains feeding systems as potentially only a down cable and immersion heater are needed in addition to the micro electric generator (eg wind or photoelectric) to enable heat generated by the micro generator to be stored for use when needed. The homeowner receives the full value of the electricity, generated by micro generation, in the form of heat that supplements their heating and/or domestic hot water system.

Instead of incurring the high losses that occur from controlling and conditioning the electrical output for mains feed, or even greater losses involved in battery storage, almost the full output is stored as heat in the thermal store reducing or even eliminating the cost of the conventional heat source as described above. Further, far from only receiving the very poor small payback per kilowatt/hr from the generating company, who generally do not want the complications involved with accepting micro generation -after all they are there for profit -the full value is received by the householder as heat. The thermal storage boiler/combj in all *,. other ways functions as a normal thermal storage boiler/combi unit as described in patent No 2266762 with heated primaiy water drawn from the thermal store for central heating and/or to provide domestic hot water via a heat exchanger. The thermal mass of the thermal store * enabling the provision of continuous heat output despite only receiving intermittent input.

Although off peak mains electricity is described as the preferred primary means of heating the thermal store it should be understood that this does not preclude any other means of heating the thermal store or the "alternative/s" source of electrical input from being the primary heat source.

Aithough "micro generation" from wind generation or photoelectric generation is described it should be understood that this does not preclude other forms of intermittent alternative/s to mains generation and or larger generation (for example village scale wind or tidal farms) to be used.

Although domestic thermal storage and micro generation has been described this does not preclude much larger thermal storage of, for example, day time photovolc or base load wind generation to be used in larger systems, for example in, district heating systems or the maintenance of night time greenhouse temperatures when the losses through the glass at far exceed that lost in the day.

In order that the invention may be more readily understood and so that further features may be appreciated the invention will now be described by way of example with reference to the accompanying drawing which is a diagrammatic representation of a form of the present invention with pipework, safety and expansion systems omitted for clarity wherein: A thermal store 1. containing a primary medium (normally water containing a proprietary reaction inhibitor) has at least part of its thermal input provided by immersion heaters 2.

and/or 3. the electrical energy for which is provided by electricity generated by sources, typically wind turbine 4. and/or photovoftajc array 5., other than mains electricity.

Additional direct or indirect input/s of flow/s and return/s from other heat source/s e.g. heated water from a boiler, heat pump, CHP unit, or solar panels, or mains powered immersion heaters may be incorporated within the thermal store to supplement or supplant the alternative inputs when needed.

The thermal store may conveniently be formed by a commercially available stainless steel unvented cylinder preferably having a capacity of greater than 100 litres. Other materials such as steel or copper or composites may be used. The store capacity may usefully be much increased to provide greater instantaneous flow rates to taps and greater thermal reserves against longer periods of supply interruptions.

All the other components described above may conveniently be those commercially available. Alternatively they may be specially fabricated from any suitable material and of any capacity to suit a specific application. * S. S. * * S. *5bS * * **. * *5 SI I * * S *

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