E30: Preheat Water Using Waste Heat from Generator – Above Green

Requirement Summary

This measure can be claimed if waste heat is recovered from a power generator running on diesel or gas fuel, to preheat water flowing into the main hot water system of the hospital. If this measure is selected, the assumptions in the Key Assumptions on the Design tab must be verified. The user must select the appropriate fuel under ‘Fuel Used for Electric Generator,’ either Diesel of Natural Gas, and input the appropriate value for ‘% of Electricity Generation Using [Fuel].’

Intention

Recovering waste heat from power generators to preheat the water supplied to the hot water system helps buildings to significantly reduce fossil fuel consumption, lower operating costs and pollutant emissions. Hospitals that use energy for hot water and that use a power generator as a significant source of electricity can reap benefits from the use of heat recovery systems such as lower maintenance, quieter operation and higher availability of hot water, as well as reducing the energy costs and the carbon emissions from lower fuel consumption.

Approach/Methodologies

Waste heat is recovered from the power generator. The percentage of electricity provided by the generator should be marked in the Design section under Advanced Settings.

Potential Technologies/Strategies

In the context of buildings, heat recovery aims to collect and reuse the process heat waste that would otherwise be lost. Sometimes, the loss of this heat is intentional, such as in air conditioning, where the purpose is to remove heat from a space. But heat is also lost in the exhaust fumes emitted by an electric generator. Using a recovery technology, this waste heat can be turned into a useful source for hot water generation by preheating the water feeding the boiler.

Relationship to Other Measures

The use of waste heat from the generator to preheat the hot water supply reduces the load on the hot water system and shows a decrease in energy use for ‘Water Heating.’

Assumptions

The default fuel for the Electric generator is Diesel, as listed in the Key Assumptions for the Base Case in the Design section. The fuel can be changed to Natural Gas if that is the fuel powering the generator. If this key assumption is changed from the default value, justification and documentation of fuel availability must be provided. Regardless of the fuel source, if the improved case uses this energy measure, it is assumed that a portion of the hot water demand is covered by the recovery of the waste heat from the generator.

Compliance Guidance

To demonstrate compliance, the design team must provide the following documentation to support their claims.

Design Stage

Post-Construction Stage

At the design stage, the following must be used to demonstrate compliance:

Manufacturer’s data sheets for generator specifying hours of operation and coverage of the demand; and
Manufacturer’s data sheets for the recovery technology used; and
Mechanical and electrical layout drawings showing the location of the generator, the recovery technology and the output for the water heating system; and
Calculation to demonstrate that waste heat covers % of the demand for hot water as calculated by EDGE software.

At the post-construction stage, the following must be used to demonstrate compliance:

As-built mechanical and electrical drawings with the location of the generator, the recovery technology and the output for hot water; and
Delivery notes and purchase receipts showing that specified generator and the recovery technology have been delivered to the site; and
Manufacturer’s data sheets for generator specifying hours of operation and coverage of the demand; or
Photographs of installed external and internal equipment related to the system.