◆  Public Baths and Swimming Pools  ◆ 

Target Heat Contribution: 70% Wastewater Heat Recovery + 30% Heat Pump

Integrated Hot Water, Heating and Cooling Designed to Replace Boilers

 

ZERO BOILER is an integrated energy system that recovers available waste heat first and uses a heat pump to supply the remaining heat required.

Conventional public baths often discharge warm bathwater and wastewater without fully recovering their heat, while boilers heat the incoming fresh water.

ZERO BOILER uses a counterflow heat recovery system designed to process the full wastewater flow. Recovered heat preheats incoming fresh water, and a heat pump supplies the remaining heating demand to reduce or replace boiler use.

1. Full-Flow Counterflow Wastewater Heat Recovery

Warm wastewater and incoming fresh water pass through separate flow paths in a counterflow heat exchanger, transferring heat without mixing the water streams.

• Wastewater heat recovery : Target contribution of approximately 70% of the required domestic hot water heating energy.

• Heat pump : Supplies the remaining approximately 30%.

 

Key functions include :

• Preheating winter mains water from 5°C to approximately 30°C under the stated operating conditions.

• Reducing hot water energy consumption by recovering heat from wastewater.

• Storing preheated water in an intermediate-temperature tank to help meet demand during bath refilling.

 

The core principle is to recover available heat before using additional energy to heat fresh water.

2. Groundwater Supply — Water Source Heat Pump

Facilities using groundwater can use a water source heat pump to take advantage of its relatively stable temperature.

Wastewater heat recovery preheats the incoming water, while the heat pump produces the hot water required for baths and facility heating.

The heat source system is designed according to groundwater temperature, available flow and site conditions.

3. Mains Water Supply — Air Source Heat Pump

Facilities using mains water can also use full-flow counterflow wastewater heat recovery.

Incoming fresh water is preheated using wastewater heat. An air source heat pump then supplies the remaining heat required for hot water and space heating.

This converts a boiler-dependent hot water system into a system centered on waste heat recovery.

4. Summer Cooling Heat Recovery

In summer, heat removed from indoor spaces is recovered for hot water production.

Conventional cooling systems release this heat outdoors. ZERO BOILER is designed to use it for hot water first.

• Uses heat rejected during cooling for hot water production.

• Minimizes additional hot water heating within the available heat recovery capacity.

• Releases excess heat outdoors after hot water demand has been met.

• Improves summer energy utilization by integrating cooling and hot water production.

While recovered cooling heat meets the hot water demand, the need for additional hot water heating can be minimized.

The compressor and circulation pumps still consume electricity. If hot water demand exceeds the available recovered heat, additional heat pump output or another heat source is required.

5. Integrated System Designed to Replace Boilers

Wastewater heat recovery, heat pumps, intermediate-temperature water storage, and heating and cooling are integrated to reduce facility energy consumption.

 

ZERO BOILER — Recover available heat first. Supply only the remaining heat required.

 

The 70% heat recovery and 30% heat pump figures are design targets for hot water heating energy. Actual contributions depend on fresh water and wastewater temperatures, available wastewater flow, operating conditions and heat exchanger performance.

 

Whether supplied by mains water or groundwater, ZERO BOILER starts with the heat that would otherwise be wasted.

 

 Winter Operation

• Uses an air source heat pump in a public bath supplied with mains water.

• Recovers wastewater heat through a plate heat exchanger to preheat incoming fresh water.

• Uses separate hot water and space heating storage tanks to supply domestic hot water and FCU heating.

• Preheats winter mains water from 5°C to approximately 30°C under the stated operating conditions.

• At a final water temperature of 36°C, this preheating represents approximately 80% of the required water heating energy.

• The heat pump supplies the remaining approximately 20% of hot water heating energy, together with the required space heating energy.

Recover available heat first, then use the heat pump to supply the balance.

 Summer Operation

• Wastewater heat recovery preheats incoming fresh water.

• The heat pump recovers heat removed during cooling and uses it to produce hot water.

• Chilled water passes through the cooling storage tank and is supplied to FCUs.

• Hot water is stored in the domestic hot water tank and supplied to the bathing facilities.

• Recovered heat that is not needed for hot water is released outdoors.

• Heat recovery and outdoor heat rejection are controlled according to cooling load and hot water demand.

Use cooling heat for hot water first. Release only the excess heat outdoors.

      ◆  Groundwater System Diagram  ◆

Public Bath Hot Water and Heating System

1. Uses groundwater as a stable heat source, supporting boiler replacement.

2. Recovers wastewater heat through a plate heat exchanger.

3. Stores medium-temperature water to meet peak demand when baths are drained and refilled.

4. Produces water at approximately 40°C for bath filling.

5. Provides summer cooling and winter heating through fan coil units (FCUs).

6. Enables boiler-free operation when sized to meet the facility’s heating and hot water loads.