Heating and Cooling Energy - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 235

ing acceptance of energy management systems for building management
applications has been pushed by federal mandates.
Appliance and equipment efficiency standards are having a notable
impact on electricity demand in the United States. Standards have low-
ered national electricity use by 3%. A few energy efficiency measures, such
as power-managed personal computers, have been widely adopted with-
out financial incentives or much utility involvement.
Energy saving systems integrate the operation and management of
heating, ventilation, air conditioning, security, light and fire safety systems
to reduce energy costs and minimize carbon dioxide emission of commer-
cial buildings. The weak link in most older systems is the dependence on
a human operator. The future vision is a building that almost runs itself,
from adjusting HVAC loads to dimming the lights.
Energy efficiency is part of an overall goal to reduce energy use and
carbon dioxide emissions. The result is practical, computerized energy
management systems that unify the operation and monitoring of heating,
ventilation, air conditioning, security, lighting and fire safety systems.
HIGH-EFFICIENCY HEATING
Some newer heating system technologies involve modifications to
conventional heat exchangers or the burn design. These changes provide
steady-state efficiencies approaching 90%, with seasonal efficiencies to
85%. This is about 10% better than the steady-state efficiencies of 78 to
80% for the most efficient conventional designs.
One newer technique uses spark ignition in the combustion cham-
ber to keep exhaust gases at 120°F instead of 400°F or more. In this pro-
cess almost all the useful heat is removed and the gases are cool enough to
be exhausted through a plastic pipe. This type of system allows seasonal
and steady-state efficiencies to reach 90%. Air and natural gas are mixed
in a small combustion chamber and ignited by a spark plug. The resulting
pressure forces the hot exhaust gas through a heat exchanger, where water
vapor condenses, releasing the latent heat of vaporization. In subsequent
cycles, the fuel mixture is ignited by the residual heat.
One system manufactured by Hydrotherm, of Northvale, New Jer-
sey, has efficiencies of 90 to 94%. The cost of the system is between 50 and
100% higher than a conventional one, but the improved efficiency can pay
back the difference in 5 years.
Conventional flame retention burners create a yellow flame, while