FI128416B - Hybrid heating system using district heating - Google Patents

Abstract

The invention relates to a hybrid heating system using district heating, comprising: - a heating circuit (22) circulating circulating water adjustable via said heat exchanger (14) heated by district heating; said heat exchanger (14) for district heating. The heat pump capacitor (30) is divided into a hot side capacitor (36b) which is adapted to supply heat to the recycled use water (VVC) circulation.

Description

HYBRID HEATING SYSTEM USING DISTRICT HEATING

The invention relates to a hybrid heating system using heating heat, comprising - a district heating primary circuit in parallel to the heating of the hot side of the water heat exchanger and a heating cycle in a heat exchanger as well as jointly with the series-connected cold water to the heat exchanger, in which the return water circuit is connected between said hot water 10 of the upper and the lower heat exchanger or a heat exchanger option, the to the cold end, - a heating circuit circulating the circulating water from the adjustable heat exchanger of said district heating, and - a heat pump circuit comprising a compressor, an evaporator and a condenser and

Especially in larger properties, in addition to district heating, it is advisable to use a heat pump with, for example, geothermal heat or exhaust air as the heat source. As district heating supply contracts always include provisions on, for example, minimum cooling of district heating water, this limits the utilization of the heat pump.

The Finnish Energy Industry Association has published publications on the application of an exhaust air heat pump (PILP) in a district heating house (Heat Use Working Group 30.10.2017; Exhaust heat pump (PILP) in a district heating house; instructions for the designer. known in connection with a accumulator.The publication discloses the heating of a heat pump

20195278 prh 05 -04- 2019 optional for hot water heating if heat is left over after the heating circuit is heated.

There is a clear problem with the basic district heating connection of a property during periods of low consumption, such as at night. The cold domestic hot water heat exchanger heats up to almost domestic hot water temperature, so that the required minimum district heating cooling is not achieved. The low heat demand of the hot water circuit keeps the district heating water flow on, which leads to the heating of the cold hot water heat exchanger10. When using a heat exchanger or a coil between the previous exchangers to transfer heat pump energy to the hot water, the problem is that the district heating return water used to heat the hot water circuit preheats the cold hot water and the heat pump energy cannot be transferred to the domestic hot water preheating to the same extent.

The object of the present invention is to eliminate said drawback and to provide a system which ensures sufficient cooling even during periods of low consumption. The hybrid system according to the invention is characterized by what is stated in the claims. The characteristic features of the invention are set out in the appended claim 1. The higher temperature of the superheated refrigerant produced by the heat pump compressor is difficult to utilize, however, the amount of heat remains quite small. In the solution according to the present invention, this lower but high-temperature amount of heat can be utilized and for this purpose its amount of heat is very sufficient. Thus, at night or at other quiet times, the hot water circulating water is heated by the heat of the superheated medium to the end temperature of the hot hot water, at which point no district heating is required at all and the cold hot water heat exchanger is not adversely heated.

Particular advantages of the invention include:

- Improves district heating cooling - Enables more efficient heat transfer of heat pump energy to domestic hot water preheating - Enables the use of heat pump energy to heat domestic hot water circulation

For safety reasons, an intermediate circuit between the hot condenser and the hot water circuit is used.

According to an embodiment of the invention, the heat of the circulating water returning from the heating circuit to the heat pump condenser is optionally used for heating cold domestic water, which is arranged by means of a second heat exchanger in series. However, the loss of degree in the countercurrent heat exchanger is small. The remote15 1 heat input valve on the hot water side only opens when there is a clear hot water consumption.

The heating circuit supplied by the heat pump and the actual heating circuit can advantageously be connected to the same circuit by using a free-flow separator, on which the flow rates are determined independently on both sides, but additional heat can be supplied by means of partial flow.

20195278 prh 05 -04- 2019

In a preferred application, a bypass line is used in the heating circuit supplied by the heat pump, by which the heat supply can be directed directly to the additional heating of the cold domestic hot water when there is no consumption in the actual heating circuit.

The invention will now be described with reference to some preferred embodiments of the accompanying figures, to which, however, the invention is not intended to be exclusively limited.

Figure 1 shows the basic connection of a hybrid system using district heating and using another heat source by means of a heat pump, here utilizing exhaust air heat.

Figure 2 illustrates a free flow separator

Figure 3 shows a more advanced hybrid system than the basic circuit of the hybrid system of Figure 1

Figure 4 shows another modification of the basic circuit of the hybrid system of Figure 1

20195278 prh 05 -04- 2019

The system of Figures 1 and 3 is first based on a basic circuit that normally uses district heating, which includes a district heating primary heat exchanger (10.1) and a heating circuit heat exchanger (14) with a district heating circuit connected in parallel and cold water (DHW) connected in series with them.

1 heat exchanger (10.2 in broken lines), in which the return hot water circulation (LVK) is connected between the upper and lower heat exchangers (10.1, 10.2) of said hot water. The conventional system comprises a heating circuit (22) circulating the circulating water from the adjustable heat exchanger (14) of said district heating. A part known per se is a heat pump circuit (30) comprising a compressor (31), a choke (32), an evaporator (34) and a condenser (36a) connected to utilize an external heat source selected by its evaporator, here the exhaust air machine (20) and alongside the heat exchanger (14) as selected. Figure 1 shows both options for the hot water heat exchanger 10, in which case a separate cold water heat exchanger (10.2) is recommended, but still optional.

According to Figure 1, the basic circuit of the invention comprises a first condenser (36b) in the heat pump circuit (30) for utilizing the amount of heat in the superheated medium. This first condenser (36b) heats the water in the intermediate circuit, which transfers the heat in the heat exchanger (16) to the hot water circuit (DHW).

20195278 prh 05 -04- 2019

Here, the heat pump circuit (30) utilizes the exhaust air by means of a machine (20). Alternatively, other available heat sources can be used, especially ground heat. The heat pump is here connected to the exhaust air unit by indirect evaporation.

The connection can also be direct vaporized, where the refrigerant circulates directly in the exhaust air coil or other heat source.

Figure 2 shows a free-flow separator (24) in which the charging input (24.1) of the heating circuit, its discharge (24.2), the additional heating input (24.4) and the additional heating output (24.3) are connected to the same volume. With this flow component, the circulating flow of the charging circuit is not disturbed by the supply flow of the auxiliary heating, but this substantially transfers the space current according to the charging current from the input current of the auxiliary heating.

Fig. 3 shows a substantially improved version compared to the basic connection of Fig. 1, the auxiliary heating return flow can be controlled in a controlled manner for auxiliary cold water (DHW) heating by means of a heat exchanger (18) in cold water heating in series with the actual hot water heat exchanger (12). By means of the three-way control valves (26) and (28), the basic heat of the heat pump from the heat exchanger (36a) can be optimally controlled to the desired destination according to the heat consumption situation.

Thus, if there is no consumption in the heating circuit, the heating produced by the heat pump can be directed to the hot water heating or vice versa.

In the variant of Figure 4, the superheat heat of the heat pump heats the domestic hot water via the heat accumulator (40). No other heat accumulator connections are shown. The first condenser (36b) utilizing the superheat heat heats the circuit which supplies heat to the top of the accumulator. The circulating water (LVK) heat transfer coil (42) is at the top of the accumulator (40), whereby the heat is transferred to the liquid of the accumulator (40).

20195278 prh 05 -04- 2019 through the circulating water heating circuit. Such a variation would be possible in which the water at the top of the heat accumulator is circulated in the heat exchanger of the DHW circulating water.

Hybrid system operation report

A control system (FIKSU®) is used to control the whole.

The control system is remotely controllable and adjustable in the FIKSU remote control room.

Hot water

In the preheating of domestic hot water, a part of the heat produced by the heat collection system that is not needed for heating is utilized.

Adjustment

Based on the flow temperature sensor measurement, the controller adjusts the control valves in series, keeping the hot water temperature at its setpoint. The setpoint is 58 ° C. The hot water control forecast function speeds up the control and reduces jitter in changes in water consumption based on the metering data of the forecast sensor. The return temperature is determined by measuring the return temperature of the hot water circuit. When the return temperature is below 55 ° C, the system reports a deviation.

DHW pump

The hot water circulation pump always runs. An alarm will follow if the pump is not running. The circulating water pump is controlled and read from the control system via the Modbus interface.

Heating circuit (IQx), Control

Based on the flow measurement, the controller controls the control valves in series, keeping the heating flow temperature at the setpoint according to the control curve.

20195278 prh 05 -04- 2019

When the heating system is equipped with a heat recovery system, the heat produced by the heat recovery system is primarily heated.

An additional heat source ensures heat adequacy. The control system optimizes the control based on energy costs. The heating circuit is either a direct heating circuit, or it acts as a preset circuit for the downstream circuits behind it. The preset circuit adapts to the settings of the post-adjustment circuits. The post-adjustment circuits 10 are made with their own controllers, which are connected to the system via a bus.

LJ pump

The operating mode of the heating circuit pump is adjustable. The pump always runs 15 or starts when the outside temperature drops below + 17 ° C and stops when the temperature rises to + 19 ° C. Conflict alarm from the pump running mode. When the pump is stopped, it is started once a week for 1 minute to prevent jamming. The circulating water pump is controlled and read from the control system via the Modbus20 interface.

District heating return limit At ⁰

When the district heating return temperature is more than 2.0 ° higher than the heating return temperature, the setpoint of the control valves 25 is compensated by keeping the difference below the desired setpoint of 3.0 °.

Yöalennus

The controller lowers the heating flow temperature. The function is activated if necessary. The amount of drop, duration and 30-week program can be changed from the controller or control room. The controller can also be used to set the automatic pre-increase in degrees and the duration of the pre-increase.

The autumn drying

The autumn time drying function automatically raises the heating flow temperature in the autumn for 20 days at a setpoint of + 3 ° C. The function is switched on when the average daily temperature has been above 5 + 7 ° C for at least 20 consecutive days and then falls below the + 7 ° C limit. The function is on for the next 20 days when the outside temperature is below +7 ° C.

Summer closing of valves

The heating control valves are closed when the outdoor temperature exceeds the setpoint of 17 ° C, the function is selectable. When the function is activated, the valves are guided open each time once a week to prevent jamming.

Heat pump LP (13x) - Heat pump control

The heat pumps are controlled from the control system via the Modbus interface.

Claims (6)

claim 1. Hybrid heating systems using district heating, the fold includes The primary circuit of the district heating comprising the parallel heating of the hot water heat exchanger (10) and a heat exchanger heat exchanger (14) and a joint in series with these coupled cold hot water heat exchangers (10.2, 12), where the recirculating water the upper and lower heat exchanger (10, 10.2, 12) of the utility water, and a heating circuit (22) which controllably circulates circulating water via the remotely heated heat exchanger (14), A heat pump unit (30) including a compressor (31), shunt (32), evaporator (34) and condenser (36a, 36b) and coupled to utilize the external heat source selected by the evaporator (34) and to supply heat with the condenser (36a) parallel to the district heat exchanger heat exchanger (14), characterized in that the condenser of the heat pump unit (30) is two-part including a heat-side condenser (36b) for utilizing heat from superheated gas and a conventional condenser (36a) arranged to provide heat with the district heat exchanger (14), and where the heat side (36b) of the condenser is arranged to supply heat in the circulation of the recycled use water (LVK). 2. Hybrid heating system according to claim 1, characterized in - 30 is characterized by the fact that there is a waterborne intermediate circuit between the condenser heat side (36b) and the use water circulation which transfers heat from the hot side condenser (36b) to the use water circulation (LKV). 3. A hybrid heating system according to claim 1 or 2, characterized in that it comprises an additional cold use water (KV) heat exchanger (18) and a control valve system (26, 28) coupled to alternatively utilize the heating system. 5 the reciprocating heat circulation of the pump. 4. A hybrid heating system according to any of the claims 1-3, characterized in that the lines supplying the heat pump heating circuit are separated from the parallel lines by a relief valve (24) which prevents changes in the constant flow in the said supply lines (24.3, 24.4) and the heating lines charge lines (24.1, 24.2). 15 A hybrid heating system according to any of the claims 1-4, characterized in that the heat source (20) used by said heat pump unit (30) is the outlet air of the building. A hybrid heating system according to any of the claims 1 to 4, characterized in that the heat source (20) used by said heat pump unit (30) is an earth heat well.