Handbook of air conditioning and refrigeration / Shan K

25.14 CHAPTER TWENTY-FIVE
For both fan-coil and water-source heat pump systems, for each ton of refrigeration capacity
there is about a corresponding 320 cfm (151 L/s) of volume flow for the small fan in the fan-coil
unit and 80 cfm (38 L/s) of volume flow in the dedicated outdoor ventilation system. The dedicated
outdoor ventilation system has often a total pressure loss of 5 in. WC (1250 Pa).
For VAV systems, the system total pressure often has a 1 in. WC (250 Pa) fixed pressure loss.
The variable part will drop to an average of its 65 percent design system total pressure loss during
part-load operation.
25.7 ELECTRICITY DEREGULATION
Electric Utilities prior to Deregulation
Electric Deregulation
�p f, in WC (Pa) � f� m� d
Constant-volume single-zone packaged system 2.5 (625) 0.40
Multizone packaged system 4.0 (1000) 0.45
VAV reheat packaged system 4.0 (1000) 0.45
VAV reheat central system 5.0 (1250) 0.55
Dual-duct VAV central system 6.0 (1250) 0.55
Fan-coil system 0.5 (125) 0.25
Water-source heat pump system 0.5 (125) 0.25
An electric utility is vertically integrated from three main components: generation, transmission,
and local distribution network, as shown in Fig. 12.11b. There are usually four kinds of generation
plants: high-efficiency coal and nuclear plants and inefficient diesel and gas-turbine plants.
Prior to the electricity deregulation, large facilities purchased electricity often based on the
time-of-use (TOU) electric rate schedule that divides a 24-h working day into two or three periods,
on-peak (such as from 9 a.m. to 10 p.m. weekdays) and off-peak periods (10 p.m. to 9 a.m. weekdays
plus weekends and holidays) or on-peak, partial-peak, and off-peak periods. Higher rates are
charged for on-peak hours than for off-peak hours. In addition, there is a demand charge and a
monthly service charge based on the largest on-peak electricity power demand. In the 1990s prior to
the electricity deregulation, unit electric rates ranged between $0.02 and $0.16 per kWh with an average
around $0.07 per kWh in the United States.
By using a time-of-use electric rate schedule, electric utilities tend to shift the electricity from
on-peak hours to off-peak hours, and they shift the daytime peak operation of inefficient diesel and
gas-turbine plants to nighttime base-load high-efficiency coal and nuclear plants to reduce operating
costs.
Electric utilites were originally regulated to prevent duplicated investments in electricity generation,
transmission, and distribution networks to serve the same community. Electricity deregulation
encourages open markets and competition and is generally considered as a means to reduce
the cost of electricity and services. According to Warwick (1997), in the United States, deregulation
began 20 years ago with telecommunications, gas, banking, airlines, and trucking. For electric
deregulation, the Public Utility Regulatory Policies Act (PURPA) of 1978 required retail utilities
to buy power from small generation plants developed by independent producers. This formed a
competitive market in power generation and power wholesalers. In 1995, the Federal Energy Regulatory
Commission (FERC) required utilities with bulk power transmission lines to provide open
access to wholesale power buyers and sellers. As of 1997, two of the three major operations, generation
and transmission, are open to competition as the result of the federal reforms. The next