The Relationship between Electricity Generation and Water Heating

In order to investigate the relationship between electricity generation and water heating in a readily comprehensible manner, let us look at the electricity generated and water heated when preparing a bath.
The values given on this page may differ from actual amounts of energy usage.

With a Gas Water Heater

When heating water for the bath using a gas water heater, in the case that 5.8kWh of energy is consumed:

• If the efficiency of the water heater is 79%, 7.3kWh of energy is required at the gas company.
• At this time, if 8.8kWh of electricity is consumed in the home, 31.1kWh of energy is also required from the power company.

In this case, to supply the amount of energy needed in the home, 29.4kWh of primary energy needs to be supplied at the gas and power companies.

With a Household Fuel Cell Cogeneration System

Let us look at the case with the same amount of energy used to heat the bath water with fuel cells.
In an actual situation, hot water is stored in the hot water tank, so the amount of energy required to heat the bath water would be different.

• The water heating efficiency of the fuel cells is 45%(HHV), so the energy required of the gas company for 5.8kWh is 12.9kWh.
• If 12.9kWh of gas is introduced as fuel at a generation efficiency of 33%(HHV), 4.3kWh of electricity is generated.
• Of the 8.8kWh of electricity required, 4.5kWh is supplied from the power company to make up the difference, which requires 10.7kWh at the power company.

With fuel cells, because water is heated at the same time as power is generated, the primary energy that needs to be supplied at the power and gas companies is 25.1kWh, an energy saving of 6.0kWh.

Fuel Cells are Clean with Advanced Energy Saving Features

As shown in the above, fuel cells, when operated as a cogeneration system, demonstrate energy savings of some 20% of the electrical and thermal energy needed in the home, while at the same time because they do not "burn" fuel, they can reduce CO2 emissions by 20-30%. With NOX emissions reduced by 60-90%, they can be considered an energy supply system which is clean and contributes to the prevention of global warming.