FIELD OF THE INVENTION

The invention relates to an energy recovery system as defined in the preamble of claim 1 for shopping centers.

BACKGROUND OF THE INVENTION

Shopping centers, i.e. large malls with grocery stores, are great energy consumers. The heating, lighting, ventilation, freezers and other cold storage spaces as well as cooled storerooms consume a great deal of electricity. Thus, the need for electrical power in a large shopping center is of the order of MWs. In general, 2-4 transformers are connected in parallel to ensure the supply of electricity, instead of operating on a single sufficiently big transformer. In other words, the set of distribution transformers may for example be constituted of three 5MW transform- ers connected in parallel. If all the transformers are continuously connected, the mere no-load power thereof is of the order of 15MW x 0.02, i.e. approximately 300kW. The power need for freezers can be considered to be 1- 2kW/m. As a large supermarket may have hundreds of meters of freezers, in addition to the other cold storage spaces and cold storerooms, the power need thereof easily ranges from 0.5 to 1MW. This entire amount of electrical energy transforms into heat which is naturally increased further by the heat energy removed from the cold spaces. It is also to be noted that such amounts of energy are released constantly and evenly, i.e. the refrigeration devices operate evenly every day around the clock. Normally, the heat dissipated from the transformers and the waste heat from the refrigeration devices are simply conveyed out from the building because no good use has been found for them. In some applications, they are used for heating purposes, if need arises in the actual shop facilities, storages or even in the parking garages. OBJECTIVE OF THE INVENTION

The objective of the invention is to remedy the above- mentioned defects of the prior art. In particular, the objective of the invention is to disclose a novel system which more effectively utilizes energy and in which the use of energy in a shopping center and the different waste energies can be optimally utilized.

SUMMARY OF THE INVENTION

The energy recovery system according to the invention is designed to be used in shopping centers with a large number of cold storage spaces cooled by refrigeration machines, such as chest freezers, upright freezers, chest refrigerators, upright refrigerators, refrigerated counters and a variety of corresponding storage spaces, as well as at least one distribution transformer to supply the electrical energy needed by the shopping center. In addition to the refrigeration machines, the greatest electricity consumers include lighting and ventilation. According to the invention, the energy recovery system includes a closed heat transfer fluid circulation including, in a sequentially connected configuration, a first heat exchanger connected to the refrigeration machines to recover the heat produced thereby, a second heat exchanger con- nected to the transformer/s to recover the heat dissipated therefrom, thirdly a solar energy collector and fourthly a microturbine coupled to a generator to produce electrical energy by the heat energy recovered to the fluid circulation from the refrigeration machines, the transformers and the sun.

In the system according to the invention, it has been rightly understood to utilize in the right order the large energy flows at different temperatures in such a way as to first recover to the fluid circulation the heat dissipated from the refrigeration machines. After this, the same fluid circulation cools the transformers operating at a higher temperature, and finally the fluid circulation can be pressurized and vaporized by suitable solar collectors. Since energy from the sun is naturally not always available, the system preferably includes an additional heating device following the solar collector. Thus, the pressure and temperature of the fluid circulation can always be adjusted to be suitable for the microturbine. The additional heating device may be for example a gas-operated or fluid-operated boiler.

The most applicable for use as solar collectors are collectors which concentrate the radiation of the sun and track the sun. With such collectors, the temperature of the fluid circulation during sunshine can be easily raised to several hundred degrees for the entire day. Preferably, the solar collectors are situated on the roof of the shopping center. This empty and free, unused space is an excellent place for solar collectors in large shopping centers. It is rare to even have any standing trees to give shade because, in general, the shopping centers are surrounded by large parking fields. At the microturbine, the temperature and pressure of the fluid in the fluid circulation decrease significantly. However, the best power for the heat exchanger at the refrigeration machines is obtained in the case where the temperature of the fluid circulation is provided very low priorly. Thus, the system preferably includes a cooling system following the microturbine to cool the fluid circulation and recover the residual heat before conveying the fluid circulation to the first heat exchanger. The cooling system used may be any suitable heat exchanger able to heat for example the greenhouses in the neighborhood, the water in the indoor swimming pool of the shopping center, some of the facilities in the shopping center, in the warming- up of incoming air etc.

In the system according to the invention, heat pumps can also be used to raise the temperature of the recovered energy above the initial temperature. Thus, the heat pump can be used instead of the normal heat exchanger and in place of the first heat exchanger, the second heat exchanger and the cooling system. The economic use of the heat pump in one or more applications referred to above should always be explored case-specifically by considering the temperatures and heat amounts prevailing in different situations and at different times.

According to preliminary calculations, the different components in the system according to the invention operate over the following temperature ranges. The temperature of the fluid circulation is 40-80°C, for example approximately 50-70°C, after the first heat exchanger. The temperature of the fluid circulation is 80-160°C, for example approximately 100-150°C, after the second heat exchanger. The temperature of the flu- id circulation is 200-400°C or even above 400°C after an effective concentrating solar energy collector.

The energy recovery system according to the invention provides considerable advantages compared to the prior art. The system according to the invention enables the large energy flows which are normally wasted for the most part to be utilized as effectively as possible. The essential feature in the system is that the ob- tained electricity can always be used in full for the shopping center' s own need to replace the purchased electrical energy, as under no circumstances will there be a situation where the electricity need would be less than the electrical power obtained by the mi— croturbine from the waste heat.

LIST OF FIGURES

In the following section, the invention will be described in detail with reference to the accompanying drawing which schematically illustrates one energy recovery system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying figure, the energy recovery system according to the invention to be used in shopping centers includes a large number of different cold storage spaces 2 where the desired low temperature is maintained by one or more refrigeration machines 1. The refrigeration machine 1 is cooled by a first heat exchanger 5 in which a closed fluid circulation 4 circulates to convey the heat out. Instead of a conventional heat exchanger, it is also possible to use a heat pump. The temperature of the fluid circulation may be over 50°C after the first heat exchanger Following this, the system includes a transformer 3 and, in connection with the transformer, a second heat exchanger 6, by means of which the no-load losses and load losses of the transformer are recovered to the fluid circulation 4. Here, too, the conventional heat exchanger can be replaced by a heat pump. After this point, the temperature of the fluid circulation may rise above 100°C. The fluid of over 100 degrees is next conveyed to a concentrating solar energy collector 7 that tracks the sun, by means of which the temperature of the fluid circulation may rise as much as to above 400°C. Following the solar collector, the fluid circulation includes an additional heating device 10, which may be for example a gas-operated or fluid-operated heating boiler. The essential feature is that it is easy and quick to turn on and off in such a way as always to be quickly available for use as need arises, when the energy obtained from the sun is not sufficient.

Next, the closed fluid circulation 4 includes a micro- turbine 8 and a generator 9 coupled on the shaft of the microturbine . The power of the generator may be 100-300k , for example 300kW.

After the microturbine 8, the temperature and pressure of the fluid circulation will have significantly de- creased, but the temperature of the fluid circulation may still be so high as not effectively to cool the refrigeration machines. Thus, the closed fluid circulation 4 further includes, prior to the refrigeration machines, a cooling system 11, by which the tempera- ture of the fluid circulation is decreased to be as low as possible. The implementation of the cooling system may vary greatly according to the structures and functions of the mall. If there is no use for the end heat, it can be removed to the air by an air heat exchanger or to the water system by a water heat exchanger. The heat can also be utilized in the interior of the mall, in any conservatories, greenhouses, in heating the water in swimming pools, drying the facilities in humid weather etc.

In the system according to the invention, the electricity generated from the dissipated heat and free energies can be used directly in the refrigeration devices of the system in full. Thus, it significantly reduces the need for purchased electricity.

The invention is not limited merely to the examples referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims.