Chapter 15 B: COMBINED HEAT AND POWER SYSTEMS Agami Reddy (rev- May 2017) Distributed energy: scope and benefits Combined heat and power (CHP) Different measures of efficiency CHP equipment Evaluation procedure of CHP benefits Sizing and screening software programs HCB 3- Chap 15 B: CHP

What is Distributed Energy? Distributed energy is power generated (and often heat captured) at the point of use. Sweitzer, June 2006 HCB 3- Chap 15 B: CHP

Distributed Generation has evolved into: Large-scale/wholesale electric power generation systems -sizes in the range of 400-1000 MW - primarily meant to sell power to an electric utility. - The sizing of such micro-grid systems is dictated by power purchase agreements rather than by site requirements of electric power and heat (Orlando, 1996); Cogeneration or industrial/agricultural combined heat and power (CHP) systems -sizes in the range of 3-50 MW - for process applications which require almost constant thermal and electric loads to be met year-round. - These systems are meant for industrial/agricultural process applications and for district energy involving large campuses as well as clusters of residential units in a single geographic region; HCB 3- Chap 15 B: CHP

Distributed Generation has evolved into: Cogeneration or building BCHP systems -sizes in the range of 50 kW-3 MW - for individual buildings and small campuses intent is to reduce electric power purchases from the local utility by either generating electricity onsite and using the waste heat to reduce boiler heating requirements, or recover the waste heat from the boiler exhaust to generate electricity Micro-CHP systems - sizes in the range of 3-20 kW -meant for individual residential and small scale applications. HCB 3- Chap 15 B: CHP

Micro- CHP Much R&D in Europe, Japan And Canada HCB 3- Chap 15 B: CHP

Combined Heat and Power (CHP) Thermal energy from a single energy source drives the DE equipment which is meant to simultaneously meet (in whole or in part) the electrical or mechanical energy (power) and thermal load of: A single building, group of buildings, a single campus: BCHP plants Process heat and power needs of industrial/agricultural unit: ICHP plants HCB 3- Chap 15 B: CHP

Fig. 11.21 Schematic diagram of a cogeneration topping steam power plant for simultaneously producing electric power and building heating HCB 3- Chap 15 B: CHP

Improved Energy Efficiency Fig. 15.9 Cogenerated vs. separate power and heat production HCB 3- Chap 15 B: CHP

Ideal System Efficiencies Fig.15.10 (a) Simple power plant (15.16) Fig.10(b) (15.17) Fig.15.10 (b) Combined cycle Power plant HCB 3- Chap 15 B: CHP

Fig. 15.11 HCB 3- Chap 15 B: CHP

(15.18) (15.19) HCB 3- Chap 15 B: CHP

(15.22) (15.23) HCB 3- Chap 15 B: CHP

Simulated loads for the large DOE school building prototype Diurnal and seasonal loads (heating, cooling and electricity) in buildings vary a great deal as against industrial loads- hence BCHP systems need proper supervisory control in order to derive full energy Savings benefits Summer Winter Simulated loads for the large DOE school building prototype in NYC (230,000 sq.ft)

Example 15.8 Evaluating Benefits of CHP HCB 3- Chap 15 B: CHP

Fig. 15.12 Schematic for the CHP system assumed in Example 15.8 HCB 3- Chap 15 B: CHP

15.12 HCB 3- Chap 15 B: CHP

(b) HCB 3- Chap 15 B: CHP

(c) HCB 3- Chap 15 B: CHP

From MAC (2005) HCB 3- Chap 15 B: CHP

HCB 3- Chap 15 B: CHP

Sizing Software Programs (only a few listed) HOMER (NREL website)- micropower optimization program for off-grid and grid-connected power systems- hour-by-hour BCHP Screening Tool (ORNL)- add on to DOE-2 simulation program CHP Optimizer (ORNL) Excel based hour by hour program for optimal sizing of primemover and absorption chiller RetScreen CHP (Canada)- Monthly bills CoGen-ReadyReckoner (Australia)- Annual or monthly analysis- primarily for ICHP systems HCB 3- Chap 15 B: CHP

HCB 3- Chap 15 B: CHP

HCB 3- Chap 15 B: CHP

HCB 3- Chap 15 B: CHP

Outcomes Knowledge of distributed energy systems and their various sub-systems and components Knowledge of the different classes of distributed generation systems Understanding of the energy benefits of using CHP for single and groups of buildings Knowledge of the different expressions for ideal power and heat generation system efficiencies Understanding the need for proper control of BCHP systems Be able to analyze benefits of BCHP against conventional separate power and heat systems Knowledge of the different types of BCHP technologies and their inter-comparison Knowledge of the different simulation software for sizing and screening of CHP systems in buildings HCB 3- Chap 15 B: CHP