7. Energy conservation

conversion factors. Emission is also observed in the reference system because of the grid electricity generation produced originally in the power plant. Emissions of the reference system are also due to the local boiler. Three factors dominate the emissions caused by CCHP: (i) electricity produced by the CCHP systems, (ii) electricity generation process of the power

The CCHP system has drawn great interest because of its potential in prolonged economic benefit with short payback on initial capital investment. However, economic benefit is not a straightforward evaluation, which depends on the equipment cost, equipment efficiency, electricity and fuel cost, building electric demand, heating and cooling load, etc. These factors depends on the local climate condition, equipment variability, budget restriction, energy saving credits, and capital incentives to use any particular type of prime mover (PM) systems. Among those, the most significant ones that affects the economics of CCHP systems are the types of PM and weather zone effect on building load. Selecting a new PM for CCHP over a reference system is not always by simple payback period analysis, the building owners or investor may inclined toward a particular PM due to any favorable capital incentives offered

Figure 5. (a) SPP, (b) AS, and (c) IRR comparison of CCHP installed building types with the reference building [32].

plant, and (iii) heat produced by the boiler.

6. Economic analysis

50 Energy Systems and Environment

The CCHP system is an effective way to save energy over customary system with separate cooling and heating systems as it uses prime mover exhaust to heat and cool the building. This provides an alternative for the world to meet and solve energy-related problems, such as energy shortages and supply security, emission control, etc. Comprehensive analysis is often warranted to decide on appropriate prime mover for a CCHP system, which relies on the tradeoffs between energy savings, environmental impacts, and economics benefit. CCHP system's energy performance is greatly depends on the site weather zone, it works with maximum efficiency where heating, cooling, and electricity demands are mostly uniform through most or all of the year. However, energy savings will be significantly high if the installation site has higher heating demand, as it is more efficient to utilize the low quality thermal energy from PM exhaust to heat the facility rather use that energy to cool the building.

Generally, the energy conservation parameter for the study is the primary energy consumption (PEC) [32]. Another parameter, referred to as site energy consumption (SEC) always increases when the CCHP is used [33]. In contrast, the PEC is a better indicator of energy feasibility because of its potential to decrease when the CCHP is operational [33]. Figure 6 shows the PEC results of the energy analysis in the case study conducted in Minneapolis, MN, where the reciprocating ICE and fuel cell showed almost similar energy (PEC) savings. All types of buildings experienced reductions in PECs when a CCHP system was adopted. When only the primary energy savings are considered in the absence of an economic analysis, all three prime movers are good options for the three building types.

CCHP reduces CO2 emissions significantly across a varying range of loads typical of microscale systems. Figure 7 shows that CO2 emissions per unit (kWh) of useful energy output results in a 61% reduction of CO2 when a trigeneration system operates at full load compared

CCHP System Performance Based on Economic Analysis, Energy Conservation, and Emission Analysis

http://dx.doi.org/10.5772/intechopen.77000

53

A case study conducted a detailed emission analysis for a CCHP system to compare it to emissions of a reference system, which is presented in [30]. Figures 8–10 summarize

Figure 8. CO2 emissions of reference building compared with CCHP installed different building types in Minneapolis,

Figure 9. NOx emissions of reference building compared with CCHP installed different building types in Minneapolis,

to a single generation system [34].

MN [32].

MN [32].

Figure 6. PEC comparison of CCHP installed building types with the reference building in Minneapolis, MN [32].
