A Combined Heat and Power System For the College of Engineering—University of Louisiana at Lafayette

This report analyzes the current economic and environmental performance of combined heat and power (CHP) systems in power interruption intolerant commercial facilities. Through a series of three case studies, key trade-offs are analyzed with regard to the provision of black-out ridethrough capability with the CHP systems and the resutling ability to avoid the need for at least some diesel backup generator capacity located at the case study sites. Each of the selected sites currently have a CHP or combined heating, cooling, and power (CCHP) system in addition to diesel backup generators. In all cases the CHP/CCHP system have a small fraction of the electrical capacity of the diesel generators. Although none of the selected sites currently have the ability to run the CHP systems as emergency backup power, all could be retrofitted to provide this blackout ride-through capability, and new CHP systems can be installed with this capability. The following three sites/systems were used for this analysis: (1) Sierra Nevada Brewery - Using 1MW of installed Molten Carbonate Fuel Cells operating on a combination of digestor gas (from the beer brewing process) and natural gas, this facility can produce electricty and heat for the brewery and attached bottling plant. The major thermal load on-site is to keep the brewing tanks at appropriate temperatures. (2) NetApp Data Center - Using 1.125 MW of Hess Microgen natural gas fired reciprocating engine-generators, with exhaust gas and jacket water heat recovery attached to over 300 tons of of adsorption chillers, this combined cooling and power system provides electricity and cooling to a data center with a 1,200 kW peak electrical load. (3) Kaiser Permanente Hayward Hospital - With 180kW of Tecogen natural gas fired reciprocating engine-generators this CHP system generates steam for space heating, and hot water for a city hospital. For all sites, similar assumptions are made about the economic and technological constraints of the power generation system. Using the Distributed Energy Resource Customer Adoption Model (DER-CAM) developed at the Lawrence Berkeley National Laboratory, we model three representative scenarios and find the optimal operation scheduling, yearly energy cost, and energy technology investments for each scenario below: Scenario 1 - Diesel generators and CHP/CCHP equipment as installed in the current facility. Scenario 1 represents a baseline forced investment in currently installed energy equipment. Scenario 2 - Existing CHP equipment installed with blackout ride-through capability to replace approximately the same capacity of diesel generators. In Scenario 2 the cost of the replaced diesel units is saved, however additional capital cost for the controls and switchgear for blackout ride-through capability is necessary. Scenario 3 - Fully optimized site analysis, allowing DER-CAM to specify the number of diesel and CHP/CCHP units (with blackout ride-through capability) that should be installed ignoring any constraints on backup generation. Scenario 3 allows DER-CAM to optimize scheduling and number of generation units from the currently available technologies at a particular site. The results of this analysis, using real data to model the optimal schedulding of hypothetical and actual CHP systems for a brewery, data center, and hospital, lead to some interesting conclusions. First, facilities with high heating loads will typically prove to be the most appropriate for CHP installation from a purely economic standpoint. Second, absorption/adsorption cooling systems may only be economically feasible if the technology for these chillers can increase above current best system efficiency. At a coefficient of performance (COP) of 0.8, for instance, an adsorption chiller paired with a natural gas generator with waste heat recovery at a facility with large cooling loads, like a data center, will cost no less on a yearly basis than purchasing electricity and natural gas directly from a utility. Third, at marginal additional cost, if the reliability of CHP systems proves to be at least as high as diesel generators (which we expect to be the case), the CHP system could replace the diesel generator at little or no additional cost. This is true if the thermal to electric (relative) load of those facilities was already high enough to economically justify a CHP system. Last, in terms of greenhouse gas emissions, the modeled CHP and CCHP systems provide some degree of decreased emissions relative to systems with less CHP installed. The emission reduction can be up to 10% in the optimized case (Scenario 3) in the application with the highest relative thermal load, in this case the hospital. Although these results should be qualified because they are only based on the three case studies, the general results and lessons learned are expected to be applicable across a broad range of potential and existing CCHP systems.

A graphical evaluation is performed for combined heat and power (CHP) systems using screening parameters for optimized performance with respect to operating costs, emissions, and energy consumption. CHP systems have the potential to reduce operating costs, emissions, and primary energy consumption when compared with electricity purchased from the grid and thermal energy produced from a boiler, and these benefits have been shown to depend on the location where the system is to be installed as well as the characteristics of the system itself. A CHP system is analyzed in 9 U.S. cities in different climate zones which differ in both the local electricity generation fuel mix and local electricity prices. Its potential to produce economic, emissions, and energy savings is quantified based on the concepts of required spark spread, emissions spark spread, and primary energy spark spread. The corresponding parameters for cost ratio, carbon dioxide emissions ratio, and primary energy ratio are plotted on a 3-dimensional graph which illustrates these potential benefits simultaneously. The location of each point on the 3-D graph indicates for a given geographical location whether the system falls within a region of multiple potential benefits from CHP technology. The results are unique to the efficiencies of the CHP system components and the alternate heating system. A simple sensitivity analysis is then conducted to examine the influence of electrical generation efficiency, the percentage of heat recovered, and the heating system on the cost, emissions, and energy savings potential of CHP systems. Of the 9 cities analyzed, Duluth, MN, is shown to have the greatest potential to provide these three types of benefits by using a CHP system. The results are most sensitive to the values of two input parameters: CHP electrical efficiency and CHP thermal efficiency. Changes in the input efficiency values are most influential when the electrical efficiency is low, and as the amount of recovered heat goes to 0, the electrical efficiency becomes the most important factor in whether a CHP shows the potential for cost, emissions, and energy benefits.

Micro CHP (combined heat and power) systems, as examples of decentralized energy systems, will play a central role in the future energy supply. This study, based on technical and economic factors, compares different micro CHP systems. A market-analysis, in Germany, revealed five different micro CHP technologies from different manufacturers. Eight representative micro CHP plants were chosen from these manufacturers for further investigation. These plants included two fuel cells, two Stirling engines, two combustion engines, one micro gas turbine, and one steam engine. Energy supply from the micro CHP plants to a single-family home was simulated. A simulation tool has been developed that calculates the annual costs of a micro CHP systems under real conditions. Economic comparison of micro CHP systems is based on thermal initial costs. Results, based on economic considerations, indicate that only a few micro CHP plants are appropriate for use in a single-family home. Most of the evaluated plants have a rated power that exceeds the energy demand of a single-family home. However, it can be stated that, in comparison with conventional condensing boilers, several technologies and products show promising economic results. Further studies will focus on objects with higher thermal demand. This study focuses on power and energy consumption within the German market and many national federal laws were taken into account. The method and the developed simulation tool are universally valid and can easily be adapted to other markets

In Japan, during the last 20 years, combined heating and power (CHP) system has been developed rapidly. In order to grasp the present condition of introduction and the existing problems of CHP system, the questionnaire survey on CHP system had been carried out at Tokyo.According to the results of investigation, it can be summarized as follows: 1) CHP system had been used widely in various sectors. The generating electricity capacity ranged several ten to several thousands kilowatt. 2) The percentage of CHP total capacity to the electricity demand peak was low and the average value for all users investigated was only 25%. 3) Gas turbine and gas engine achieved 60%-80% overall energy utilization efficiency with 20%-34.5% generating electricity efficiency and 19.5%-50% exhaust heat utilization efficiency. 4) Education buildings had the maximum average generating electricity efficiency with 30.6%, followed by hospital buildings with 29.6%, amusement facilities with 29.5%, office buildings with 28% and compound buildings with 25%. Hospitals attained the maximum average exhaust heat utilization efficiency with 46.1%, followed by offices with 41.3% and compound buildings 39.8%. 5) Various users had different motivation of selecting CHP system. Both office and compound buildings selected economy as the most important reason introducing CHP system; while hospital and education users concerned more saving energy. Hospital and office users were satisfied with the CHP system introduced; while compound building users were not satisfied very much with the CHP system

Combined heat and power (CHP) or cogeneration systems provide both electricity and useful heat to a building. CHP systems can result in lower operational cost, primary energy consumption (PEC), and carbon dioxide emissions when compared to the standard alternative of purchasing electricity from the grid and supplying heat from a boiler. However, the potential for these benefits is closely linked to the relationship between the ratio of power to heat supplied by the CHP system and the ratio of power to heat demanded by the building. Therefore, the benefits of the CHP system also vary with the size of the prime mover. In the model presented in this paper, the CHP system is base-loaded, providing a constant power-to-heat ratio. The power-to-heat ratio demanded by the building depends on the location and the needs of the building, which vary throughout the day and throughout the year. At times when the CHP system does not provide the electricity needed by the building, electricity is purchased from the grid, and when the CHP system does not provide the heat needed by the building, heat is generated with a supplemental boiler. Thermal storage is an option to address the building’s load variation by storing excess heat when the building needs less heat than the heat produced by the CHP system, which can then be used later when the building needs more heat than the heat produced by the CHP system. The potential for a CHP system with thermal storage to reduce cost, PEC, and emissions is investigated, and compared with both a CHP system without thermal storage and with the standard reference case. This proposed model is evaluated for three different commercial building types in three different U.S. climate zones. The size of the power generation unit (PGU) is varied and the effect of the correspondingly smaller or larger base load on the cost, PEC, and emissions savings is analyzed. The most beneficial PGU size for a CHP system with the thermal storage option is compared with the most beneficial PGU size without the thermal storage option. The need for a supplemental boiler to provide additional heat is also examined in each case with the thermal storage option.

In recent years there has been an increasing interest in the incorporation of distributed energy resource (DER) systems such as combined heat and power (CHP) and combined cooling, heating, and power (CCHP) in commercial building applications as they have shown considerable environmental and financial benefits when compared to conventional energy generation. This paper aims to investigate the potential energy, carbon emissions, and financial impact of the size of co/tri-generation systems on a real case scenario of an existing UK hotel. The analysis is carried out using Thermal Analysis Simulation software (TAS) and a payback methodology is adopted to carry out the financial analysis. The results show that the average percentage decrease in carbon emissions with CHP is 32% and with CCHP it is 36%. Whilst both CHP and CCHP systems increase energy consumption in the building, the costs are reduced, and a CHP system contributes to a higher percentage of cost savings and shorter payback periods. The incorporation of a CCHP system leads to lower energy consumption for a similar-sized CHP system. Further simulations under future climate projections revealed that a CCHP system outperforms a CHP system.

This study deals with the exergetic performance assessment of a combined heat and power (CHP) system installed in Eskisehir city of Turkey. Quantitative exergy balance for each component and the whole CHP system was considered, while exergy consumptions in the system were determined. The performance characteristics of this CHP system were evaluated using exergy analysis method. The exergetic efficiency of the CHP system was accounted for 38.16% with 49 880 kW as electrical products. The exergy consumption occurred in this system amounted to 80 833.67 kW. The ways of improving the exergy efficiency of this system were also analysed. As a result of these, a simple way of increasing the exergy efficiency of the available CHP system was suggested that the valves-I–III and the MPSC could be replaced by a 3500 kW-intermediate pressure steam turbine (IPST). If the IPST is installed to the CHP system (called the modified CHP (MCHP) system), the exergetic efficiency of the MCHP system is calculated to be 40.75% with 53 269.53 kW as electrical products. The exergy consumption is found to be 77 444.14 kW in the MCHP system. Copyright © 2006 John Wiley & Sons, Ltd.

Meeting energy demands at crucial times can often be jeopardized by an unreliable power supply from the grid. Local, onsite power generation, such as combined heat and power (CHP) systems, may safeguard against grid fluctuations and outages. CHP systems can provide a more reliable and resilient energy supply to buildings and communities while it can also provide energy-efficient, cost-effective, and environmentally sustainable solutions compared to centralized power systems. With a recent increased focus on biomass as an alternative fuel source, biomass-driven CHP systems have been recognized as a potential technology to bring increased efficiency of fuel utilization and environmentally sustainable solutions. Biomass as an energy source is already created through agricultural and forestry by-products and may thus be efficient and convenient to be transported to remote rural communities. This paper presents a design and feasibility analysis of biomass-driven CHP systems for rural communities. The viability of wood pellets as a suitable fuel source is explored by comparing it to a conventional grid-connected system. To measure viability, three performance parameters—operational cost (OC), primary energy consumption (PEC), and carbon dioxide emission (CDE)—are considered in the analysis. The results demonstrate that under the right conditions wood pellet-fueled CHP systems create economic and environmental advantages over traditional systems. The main factors in increasing the viability of biomass-driven CHP (bCHP) systems are the appropriate sizing and operational strategies of the system and the purchase price of biomass with respect to the price of traditional fuels.

Combined heating and power (CHP) and combined cooling, heating, and power (CCHP) systems generate electricity and usable heat on-site from one fuel source while organic Rankine cycles (ORC) generate power from low-temperature heat sources. During the operation of CHP and CCHP systems, there are many instances when the recovered exhaust heat is greater than the required thermal load of the building. In these situations, an ORC can be used to capture the excess heat in order to produce additional electricity. Therefore, combining an ORC system with a CHP system (CHP-ORC) or a CCHP system (CCHP-ORC) can further increase the fuel utilization of the system, thereby reducing the operational costs, primary energy consumption (PEC), and carbon dioxide emissions (CDE). This article examines the economic, energetic, and environmental performance of CHP-ORC and CCHP-ORC systems under the operational strategies of follow the electric load (FEL) and follow the electric load with the option of turning off (FEL/OFF) for the city of Boulder, Colorado. Their performance is compared to a stand-alone CHP and CCHP system, respectively, between systems, and to a reference building. Results show that under the FEL operation, the addition of an ORC to either the CHP or CCHP system lowered the operational costs, PEC, and CDE by about 12 per cent, 13 per cent, and 17 per cent, respectively, from the standalone system. In addition, only when the systems operate FEL/OFF strategy minimizing cost or PEC, the cost and PEC could be reduced below the levels of the reference building.

Examination of the optimal operation of building scale combined heat and power systems under disparate climate and GHG emissions rates

Comparative economic analysis of gas turbine-based power generation and combined heat and power systems using biogas fuel

Supply of corn stover to produce heat and power for a typical 170 million L (45 million gallon) dry mill ethanol plant is proposed. The corn ethanol plant requires 5.6 MW electricity and 52.3 MW process heat, which creates an annual stover demand of as much as 150 million Mg (Mg = 1,000,000 g = 1 metric ton). The stover supply system consists of collection, pre-processing, transportation and on-site fuel storage and preparation to produce heat and power. Economics of the entire supply system was conducted using the Integrated Biomass Supply Analysis and Logistics (IBSAL) simulation model. Corn stover was delivered in three formats (square bales, dry chops and pellets) to the ethanol plant. Among the three formats of stover supply systems, cost of chopped biomass was highest due to the high transportation cost and low bulk density. The economics of the stover fired heat generation system was assessed using a discounted cash flow method and compared with coal- and natural gas-fired systems. Although the capital investment cost of natural gas-fired heat generation system was relatively low, annual operating costs were the highest compared to the stover and coal-fired heating system. The coal-fired heating system had the lowest annual operating cost due to the low fuel cost, but had the highest environmental and human toxicity impacts. Combined heat and power (CHP) generation systems have high thermal efficiency, onsite power utilization and lower environmental impacts than process heat generation systems. A corn-stover-fired CHP plant was proposed to supply both power and process heat for the corn ethanol plant. The proposed CHP system required 137,450 Mg stover to generate 9.5 MWe of power and 52.3 MWth of process heat with an overall CHP efficiency of 83.3%. Economic analysis of the stover-fired CHP system was compared with that of both coal and a combination of coal and stover fuel options along with an environmental impact analysis. Annual savings from the CHP plant were calculated by comparing the existing energy input conditions for the corn ethanol plant. The stover-fired CHP system would generate annual savings of US $3.61 million with a payback period of 6 years. The economics of the coal-fired CHP system were relatively attractive compared to the stover-fired CHP system. but greenhouse gas emissions for the coal-fired CHP system were 20 times greater than that of stover-fired CHP system. Co-firing of stover with coal may balance out the environmental impacts and economics of the CHP system. We envision that creating demand for biomass will build infrastructures to deliver biomass fuel, which will further reduce the cost of biomass

A combined heat and power (CHP) system is an efficient and clean way to generate power (electricity). Heat produced by the CHP system can be used for water and space heating. The CHP system which uses hydrogen as fuel produces zero carbon emission. Its’ efficiency can reach more than 80% whereas that of a traditional power station can only reach up to 50% because much of the thermal energy is wasted. The other advantages of CHP systems include that they can decentralize energy generation, improve energy security and sustainability, and significantly reduce the energy cost to the users. This paper presents the economic benefits of using a CHP system in the domestic environment. For this analysis, natural gas is considered as potential fuel as the hydrogen fuel cell based CHP systems are rarely used. UK government incentives for CHP systems are also considered as the added benefit. Results show that CHP requires a significant initial investment in return it can reduce the annual energy bill significantly. Results show that an investment may be paid back in 7 years. After the back period, CHP can run for about 3 years as most of the CHP manufacturers provide 10 year warranty.

In the last decade, technological innovation and changes in the economic and regulatory environment have resulted in increased attention to distributed energy systems (DES). Combined heating and power (CHP) systems based on the gas-powered internal combustion engine (ICE) are increasingly used as small-scale distribution co-generators. This paper describes an innovative ICE-CHP system with an exhaust-gas-driven absorption heat pump (AHP) that has been set up at the energy-saving building in Beijing, China. The system is composed of an ICE, an exhaust-gas-driven AHP, and a flue gas condensation heat exchanger (CHE), which could recover both the sensible and latent heat of the flue gas. The steady performance and dynamic response of the innovative CHP system with different operation modes were tested. The results show that the system’s overall efficiency could reach above 90% based on lower heating value (LHV) of natural gas; that is, the innovative CHP system could increase the heat utilization efficiency 10% compared to conventional CHP systems, and the thermally activated components of the system have much more thermal inertia than the electricity generation component. The detailed test results provide important insight into CHP performance characteristics and could be valuable references for the control of CHP systems. The novel CHP system could take on a very important role in the CHP market.

The development of highly compact and energy-efficient systems is critical for world energy security and technology leadership. Due to the abundance of natural gas, the natural gas fueled distributed energy systems that lower the energy consumption and utility costs would be ideal in the U.S. as well as worldwide markets. To meet these objectives, researchers from Enginuity Power Systems (EPS) are currently working on the development of an ultra-efficient Combined Heat and Power (CHP) system for residential and commercial applications. These CHP systems generate electricity at the point of use while also meeting the space and water heating demands. Furthermore, a single CHP system replaces the conventional electricity generator, space, and water heating systems in residential and commercial applications. The main technical objective of this research article is the demonstration of the fundamental design and performance characteristics of an EPS’s 6 kW–10 kW CHP system intended for residential applications. The proposed residential system utilized a mirror-balanced, patented, inwardly opposed piston, four-stroke internal combustion engine as a prime mover. This novel four-stroke opposed piston design resolved the scavenging, cooling, and lubrication issues faced by the conventional opposed designs in the market while also maintaining the power density, balancing, and performance benefits. Initially, a series of experiments were conducted on the proposed system for different speeds and throttle openings. Later, the combustion, performance, and quantified energy loss pathways were presented at Wide Open Throttle (WOT) conditions to demonstrate the performance benefits of the proposed system. Finally, a performance-oriented framework was developed for the proposed CHP system for future efforts.