Page 53 - Sustainable On-Site CHP Systems Design, Construction, and Operations

32 CHP B a s i c s

Price ($/kW)
1000
$ CT price RE price

800 $ $
$ $
$ $
600 $
$
400 $ $ $ $
$ $ $
$
200
0 1 2 3 4 5 6 7
Size (kW, thousands)

FIGURE 2-4 Price of prime mover technology. [Note: Actual purchase prices may vary due to
market conditions and other factors. Prices do not include gas compressors (if required).] [From
Hedman (2001); source: Gas Turbine World/SFA Pacifi c/GRI.]

Typical costs of each prime mover shown in Fig. 2-4 provide a convenient cost com-
parison of gas turbine and reciprocating engines. It should be noted that the cost shown
is the equipment cost only and not fully constructed system.
In deciding on the type of the prime mover, the designer can also consider taking
into account the following: Combustion gas turbines have the advantage of higher ther-
mal waste heat than reciprocating engines and the ability to generate high-pressure
(HP) steam. These make combustion gas turbines attractive in industrial facilities with
high thermal energy needs. In commercial applications, however, a high electrical
generation efficiency is typically more desirable which makes reciprocating engines
more applicable (and cost-effective) for these applications.
In contrast to industrial applications, which need HP and/or LP (low-pressure)
steam, commercial buildings typically need hot water (or LP steam) for space heating
and DHW. Reciprocating engines can effectively meet these requirements. It is impor-
tant to indicate that hospitals need higher-pressure steam for sterilizers, but the capacity
and the annual usage is relatively low as compared to the total thermal energy use. In
order to satisfy this need, it is likely more efficient to design a system with a small HP
steam generator dedicated to sterilizers. Reciprocating engines are well suited for pack-
aged CHP in commercial and light industrial applications for less than 5 MW (EPA 2002).

References
ASHRAE, 2003. HVAC Applications, Chapter 35, Energy Use and Management, ASHRAE
Atlanta, GA.
ANSI/ASHRAE/IESNA, 2007. Energy Standard for Buildings Except Low Rise
Residential Buildings, ASHRAE, Atlanta, GA.
Bluestain, J., 2001. Memo addressed to the Distributed Generation Workshop of the
Regulatory Assistance Project regarding the calculations of CHP thermal output in
an output-based system, Arlington, VA, Energy and Environmental Analysis, Inc.