EP0736160A1

EP0736160A1 - Boiler with storage

Info

Publication number: EP0736160A1
Application number: EP95903467A
Authority: EP
Inventors: Arild Hardeng
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-12-06
Filing date: 1994-12-06
Publication date: 1996-10-09
Also published as: AU1250995A; WO1995016169A1; NO179424B; NO934438L; NO179424C; NO934438D0

Abstract

Method for operating a heat storage and a heat storage in which a combustion chamber is arranged in a box (3) adapted for insertion in a water storage (1), a room containing an amount of water being arranged between the combustion chamber (2) and the box (3), at least one thermostat valve (10) being arranged in the top of the box adapted to let water out from the internal of the box to the storage water above the box (3) when a preset temperature is achieved, and that a pipe (4) is extending from substantially the bottom of the storage (1) and to the interior of the box (3), above the combustion chamber (2).

Description

Boiler with storage

The present invention is related to a heat storage or a boiler with storage.

Water in tanks or storages have been used to accumulate energy. Such storages often are used in connection with boilers or kettles heated with wood, solar heating systems, heat pumps etc. and to utilize the electric tariffs in the best possible way. Accumulators store energy from the time the energy is available, until the time the energy is utilized.

Such accumulating tanks may be provided as closed systems having expansion tanks or as open systems with open possibility of expansion. The tanks further physicly may be constructed with circular or rectangular cross sections.

Primarily such accumulator tanks are used for general heating of buildings and also for provision of heated consumption water. Today such accumulator tanks frequently are used in connection with central kettles for heating with wood, sun heating and accumulation of electric energy. Typical for this is the use of modern kettles for wood, used for heating where the efficiency of the kettle is larger than the need of energy from the building. Correspondingly accumulator tanks are used for 5 storing energy transformed from electric energy.

It is probable that accumulator tanks in the future will be used as a central element in the energy system of a building. It also is probable that development will focus on rectangular storages' being insulated on the construction site. o Such storages occupy minimum floor space and very easily may be insulated. Additionally the dimensions make them easy to handle and to transport.

Traditional use of kettles for wood firing and oil in connection with accumulation of energy has been to connect the 5 kettle to the storage by pipe couplings and the other side to make the water volume of the kettle so large that boiling in the kettle to a certain degree is avoided.

Modern kettles for wood firing which typically are based on the principle of the blue flame burners, have very large capacity, in the range of 10 to 70 kW and in practical operation they must work towards a heat storage or a larger kettle volume to avoid boiling. Kettles for separate domestic houses with large water volumes, very rarely are greater than 300-4001. The space s for wood in the kettles is typically 30 200 1. With such a wood volume the kettle very quickly may come to boiling as the kettle effect exceeds the heating requirement from the house. Due to this, air supply must be strongly limited when the kettle comes close to boiling, which again means incomplete combustion o resulting in contaminations and it also may result in the fire in the kettle dying out, whereby the kettle has to be emptied before it again can be set in operation.

The alternative to the solution described above is that the kettle is connected with a water storage having sufficient s volume so that the kettle may be maintained in operation without any chance of boiling. This opens also for heating with wood, maintaining the comfort of the central heating system. With sufficient storage capacity, wood may be used for example once a week. o The development for wood firing kettles extend towards kettles having small water content and as little ceramics weight as possible in the combustion zone. The reason for this mainly is that such kettles very rapidly reach correct working temperature, thereby providing a minimum of contamination and 5 also that only a small effect is connected to the kettle itself. A kettle of the known type has a very large water volume and a ceramics weigh which binds 27 kWh before it comes up in the correct working temperature, lasting about 1% hours. In another embodiment only 8 kWh is bound up and the working temperature is 0 achieved after 15-20 minutes.

A kettle may connected to an accumulator tank in a number of ways. The most known and simple connection principle is based on a constant circulation through the kettle and the storage. This means, however, that the kettle is not sufficiently 5 warm before the storage is partly loaded, resulting into condensation in the kettle due to low temperature.

The normal connection between the storage and the kettle is use of a charging pump and a thermostat valve ensuring the internal circulation in the kettle until the operation temperature i achieved and where cold water from the storage gradually is drawn from the storage. The disadvantage with this connection is that the residual energy of the kettle cannot be exploited. As mentioned above, relatively large residual energies

5 can be found in the kettles. Within this branch, very little attention has been paid to this problem and substantially only development of the degree of the efficiency has been focused. Kettles exist with efficiency degrees of 80 - 85 % during full operation, whereas residual energy in the kettle very often ιo exists with 35 %, with traditional charging connection to a thermostat valve.

To avoid too large residual energy, so called professional couplings are used. Here the energy is drawn from the kettle before energy is drawn from the storage. The coupling is provides substantially higher degree of efficiency for the system than the traditional charge connections. With a kettle having a high degree of efficiency, a professional coupling and correct dimensioned storage, it is possible to achieve efficiency degrees for the system of about 75-80 %. The objections to this system,

20 however, are that it costs substantially more than other embodiments, to a much larger extent also claims a expertise when installing, and to a higher degree is subjected for wear, faulty use, etc.

With the present invention the above mentioned

25 disadvantages are avoided, whereby the substantial advantages are maintained. This is achieved with the kettle according to present invention as defined with the features stated in the claims.

The drawing discloses in figure 1 schematically a section along I-1 in figure 2 and figure 2 discloses a front

30 view, partly in section, of the kettle in figure 1.

In the kettle according to the present invention, the kettle 2 itself is inserted into the storage 1. Furthermore, the kettle 2 comprises a completely or partly insulated box 3, effecting the water in the box 3 is heated first. The insulation

35 11 may be secured to the outside of the sides and the bottom of the box 3. This ensures quick heating and avoids a longer period with a "wet" kettle in the heating phase. Through a sucking pipe 4 water is drawn up to the box 3 such that it is possible to charge the entire storage 1. Without such a device the heating would stop due to stratifications in the water, after the water above the kettle 2 has been heated.

When the water in the box 3 is sufficiently heated, the water is let out to the upper portion of the storage by means of thermostat valves 10 which gradually open when the water temperature in the box 3 increases sufficiently. New and cold water from the bottom of the storage 1 is drawn into the box 3 by means of the sucking pipe 4 and replaces the water which is drawn up to the top of the storage. This process continuous until the storage 1 is completely charged or until a desired charging degree is achieved, by which thermostats may be controlled, which may be arranged at different levels in the storage.

This device may be based on the principle that hot water is ascending (self circulation) or by the use of a circulation pump. Figure 1 discloses schematically a coupling with a circulation pump 7. If such a circulation pump 7 is used, the coupling would be made such that the circulation pump circulates the water in the kettle part 3 in the starting phase, until the working temperature is achieved and thereafter the thermostat valve 8 gradually will let water out of the upper portion of the storage 1 and simultaneously draw new water in, through the riser 4.

The self-circulation principle can be combined with a pump 7, a propeller or such, for internal stiring of the box. This will avoid that the hot water in the box to an unacceptable degree is ascending up to the top of the box in such a way that the lower surface of the kettle is too cold.

By a self circulation principle, the riser may be extended above the bottom of the box in such a way that the cold water drains relatively high up in the box. This will ensure an internal stiring in the box when the cold water sinks and mixes with the already heated water. For further to stir the water, baffle plates may be arranged. The box may be insulated on the outside and/or inside to avoid the metal surfaces of the box to function as heat exchangers against the cold system water. Even the upper surface of the box 3 may be insulated, because the residual heat in the kettle can penetrate into the system water even if the thermostat valves should be closed. Furthermore the box itself may be made of insulating .material.

By use of the kettle according to the present invention a substantial cost safing is achieved, by production of the kettle, in relation to kettles having traditional structure and in relation to the effect of the kettle. Further the degree of effect for the system approximately will be equal to the degree of the effect for the kettle as all energy is maintained within the insulation of the storage. Today effect degrees for systems are achieved not higher than 70-80 % with effect degrees for kettles at around 85 %.

The kettle and the storage as such may be delivered as a complete single unit directly to the construction site. The risk for faulty connections of the security equipment for the kettle and the storage thereby is substantially reduced. With the kettle according to the present invention, the kettle can be provided with an oil burner in the lower door and later modifications are substantially simplified by use of the embodiment according to the invention, having the kettle inserted in the storage.

Claims

Patent Claims

1. Heat storage, CHARACTERIZED IN a combustion chamber being arranged in a box (3) adapted for insertion in a water storage (1), a room containing an amount of water being arranged between the combustion chamber (2) and the box (3), at least one thermostat valve (10) being arranged in the top of the box adapted to let water out from the internal of the box to the storage water above the box (3) when a preset temperature is achieved, and that a pipe (4) is extending from substantially the bottom of the storage (1) and to the interior of the box (3), above the combustion chamber (2).

2. Storage according to claim 1, CHARACTERIZED IN the sides and the bottom of the box (3) are externally insulated.

3. Storage according to claim 1-2, CHARACTERIZED IN at least the sides and the bottom of the box (3) are made of a insulating material.

4. Storage according to claims 1-3, CHARACTERIZED IN electrical energy or another type of energy, such as from burning of wood or oil, is supplied to the combustion chamber.

5. Method by starting and operating the heat storage according to claims 1-4, CHARACTERIZED IN thermostat valves (10) in the top of the box ensuring internal circulation when closed, until the water temperature in the box has achieved a preset level, and that water after that is drawn to the interior of the box above the heating unit, from the bottom of the storage, through a riser (4), thereby to ensure circulation of the water in the storage after the water temperature in the box has reached a minimum temperature.

6. Method according to claim 5, CHARACTERIZED IN water being drawn from the upper portion of the box and supplied through a thermostat valve to the upper portion of the storage when the thermostat valve opens by reaching the minimum temperature.

7. Method according to claim 6, CHARACTERIZED IN water being drawn by means of a pump (7) through a throttle valve (9) and distributed to the lower portion of the box until the thermostat valve (8) opens, from which moment the water will be pumped to the upper portion of the storage.

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