The United Nations World Water Development Report claims that more than 6 billion people will suffer from clean water shortage by 2050. This is a result of climate change, demand increase for water, increase of water pollution, increasing population, and reduction of water resources [1]. In order to delay / prevent water scarcity, humans must take action using less water or perhaps recovering wastewater. Aerobic digestion is one of the best common methods to treat wastewater; however, this technology requires heavily on the use of electric motors and is estimated to consume 2–3% of US electricity. In this paper, a multigeneration energy system is developed to treat wastewater using a net-zero energy building model. This system consists of four major sub-systems: an aerobic digester, an anaerobic digester, a Brayton cycle, and a Rankine cycle. Using anaerobic digestion to produce bio-fuels, which can then be used on-site to power aeration systems, may offer significant advantages to reduce electricity usage. This study shows that the required energy for a sample aeration case study process can be supplied by a multigeneration system. Parametric analyses are performed to show how system efficiency may be increased as well as to investigate the required oxygen and power for an activated sludge process in a wastewater treatment plant. It is found here that the proposed CHP system can produce 6 times more energy than the required energy for the aeration in the activated sludge process.

Traditional combined heat and power (CHP) units should run in the heat-controlled mode. The adjustable range of power load is restricted by the heat load, and the minimum power load increases with the heat load. Because of high penetration of intermittent renewable power, operational flexibility of CHP units is highly required. It is necessary to adopt some technical solutions to realize heat-power decoupling for CHP units. To find a heat-power decoupling method with low investment and high energy efficiency, the steam ejectors, simple in structure and low in cost, are applied to design a novel heat-power decoupling system in this study. Steam ejectors can recover the waste heat of exhaust steam of steam turbines. Therefore, the integration of steam ejector may realize heat-power decoupling and energy saving simultaneously. Three heat-power decoupling systems with steam ejectors are designed. The heat-power decoupling performance and energy consumption characteristics of these systems are investigated with a reference 330 MW coal-fired CHP unit. Results show that all three modified systems can realize heat-power decoupling. The heat-power decoupling performance of improved system III is the best, and improved system I has the least coal consumption rate for power generation.

Cement industry consumes high energy levels with 4GJ per ton produced in average, 30% of it being electric and 70% thermal [1]. Cogeneration in this type of processes is not widespread; for only a few efforts have been made worldwide to implement methods that take advantage of waste heat stream, given that these contain 36% of the thermal input energy required to produce electricity [2]. Furthermore the implementation of a power generation alternative to feed limestone’s calcinations process is suggested. This paper is focused on the evaluation of thermal energy recovery strategies through the implementation of cogeneration systems, enabling an increase in efficiency and profitability producing electricity in before and after-processes of the cement production process. This will be achieved using methods of computer analysis implementing the ASPEN HYSIS™ software to simulate the behavior of the systems taking the rotary kiln operating conditions as main input or output variables. For the implementation of the system two important steps furnace operation will be taken. First one, related to combustion, is performed to produce the energy required in limestone’s processing entering this system, at this point the commercial gas turbine is used, coupled to a generator subsequently taking the power of oxygen-rich flow at the exhaust which is at a high temperature allowing a post-combustion using an afterburner. Finally, a second stage is evaluated at the downstream of the kiln, where a flow of charged waste gases counts with enough energy to perform an additional phase of power generation using an organic Rakine cycle (ORC).

In this work different concepts are investigated for combined heat and power production (CHP) from offshore gas turbines. Implementation of such technology could improve energy efficiency of offshore oil and gas production and lead to reduced fuel consumption and resulting CO 2 emissions. Offshore electric power is in most cases generated by gas turbines operating in a simple cycle. However it would be desireable to increase energy efficiency by adding steam or CO 2 bottoming cycles to produce power from the exhaust heat. However part of the heat from the gas turbine exhaust is normally used for onboard process heat for the oil/water separation process among others, this must be taken into consideration when estimating capacity for additional power production. Different CHP concepts will be evaluated at different operating conditions while running the turbines in both design and off-design mode The results show that it is possible to produce an additional 6–8 MW of electrical power from a 32 MW turbine (depending on the conditions) while using 15 MW of heat from the exhaust for on-board processing.

Combined heat and power (CHP) systems are widely used considering the prevention of global climate change and the reduction of energy costs. In distributed CHP systems, both high efficiency of elements and good coordination of the systems are considered as the points to solve. We had been researched and demonstrated the micro gas turbine CHP system with heat storage at Sapporo City University from April 2006 to March 2010. At first, the start times of microturbine (MGT) and heat storage system (HST) was set up by schedule timers. In 2008 the schedule timers were substituted to a new programmable logic controller (PLC) and the start times of MGT and HST were calculated as the function of temperature outside and room temperature. Setting the start time of MGT at maximum 5 hours before 8:00 and interlocking relays of HST on MGT, the start times were calculated from temperature outside and room temperature at 21:00 the day before. Control of start time using PLC was demonstrated from Feb. 21, 2009 to June 1 and from Nov. 16 to Jan. 7, 2010. It is shown the time series data of temperature and analysis of the CHP with the original boiler heating system.

This paper shows the main results from a technical and economical study for the implementation of new cogeneration systems in Mexican refineries. At least three cogeneration alternatives to match a 50% additional energy requirement (thermal and electric) for a refinery are analyzed. A balance simulator tool developed specially for the electric and steam refinery systems is used in order to obtain the technical parameters for the alternatives, which allows obtaining system performance indicators such as fuel consumption, cooling water requirement, electric and combined efficiency. Standard techniques as net present value, internal rate of return, and payback period are used for the economic analysis. According to the results, the best alternative was a gas turbine-heat recovery steam generator arrangement fueled by natural gas, including the respective adjustments of the refinery electrical and steam systems.

Cooling, Heating, and Power (CHP) systems are a form of distributed generation that can provide electricity while recovering waste heat to be used for space and water heating, and for space cooling by means of an absorption chiller. CHP systems improve the overall thermal energy efficiency of a building, while reducing energy consumption. Since energy conservation has implications on energy resources and environment, CHP systems energy performance should be evaluated based on building primary energy consumption. Primary energy consumption includes the energy consumed at the building itself (site energy) plus the energy used to generate, transmit, and distribute the site energy. The objective of this investigation is to determine the effect of the power generation unit (PGU) size on the energy performance of CHP systems. Since CHP systems energy performance varies with the building energy profiles, in this study the same building is evaluated for three different cities with different climate conditions. This paper includes simulation results for the cases when a CHP system operates with and without a primary energy strategy. Results show that for any PGU size energy savings are guaranteed only when the primary energy strategy is applied. Since CHP system energy performance depends on the building energy use profiles, which depend on climate conditions and other factors such as building characteristic and operation, each case requires a particular analysis in order to define the optimum size of the power generation unit.

Successful cogeneration system design requires a combination of engineering, investigation, and forecasting skills. Operating schedules for the facility must be considered in the design of the cogeneration system to optimize overall plant utilization and economics. This results in tradeoffs between electrical power production and thermal heat recovery for many applications of the technology. Optimizing these two parameters requires a thorough understanding of how and when the facility uses power and heat and the owner’s objectives of the investment in the cogeneration system. Customer-sited cogeneration systems have been accepted as one option to mitigate electrical supply shortages. On the utility side, this requires that cogeneration systems operate at a relatively high capacity factor, especially during peak periods. On the customer side, the cogeneration system must be capable of meeting onsite energy needs to reduce energy costs. In California, the Self-Generation Incentive Program (SGIP) provides incentives for the installation of distributed generation systems. Incentives are paid on an installed capacity basis ($/kW) that varies by installed technology. Eligible technologies include photovoltaic, wind, fuel cells, internal combustion engines, and microturbines. Alternative Energy Systems Consulting, Inc. (AESC) provides technical support services to the SGIP, the sponsoring utilities and SGIP’s Working Group. The services that AESC provides varies with utility, but primarily includes program design support, regulatory review, technology evaluation, application review, generator performance metering, participant training and equipment field verification. Itron evaluates the SGIP to quantify performance of the systems and estimate overall impacts of the program. This paper will present best practice recommendations for cogeneration system design to meet the efficiency criteria of the SGIP. Recommendations are based on findings from numerous AESC performance reviews and on-site inspections, as well as results of Itron’s in-depth performance evaluation of the effectiveness of useful thermal energy recovery of on-site cogeneration systems receiving incentives from the SGIP. Information is presented through Program Year 2005. Results of several past studies have suggested that cogeneration systems were not operating as they were designed and, more importantly, were not achieving the efficiencies claimed at the design stage. This paper will also explore some of the key drivers behind the unexpectedly low thermal energy recovery and overall plant performance sampled from the fleet of SGIP cogenerators. Results from recent Itron studies will be combined with AESC’s expertise in actual operations to develop a list of best practices to be followed when designing and commissioning a cogeneration system.

A model of a Micro Gas Turbine system for cogeneration is presented. The analyzed plant is based on an aero derivative Gas Turbine with a single staged centrifugal Compressor and an axial Turbine with two stages. The net power output is 260 kWe in simple cycle mode. Exhaust gases can be sent to a counter flow surface compact heat exchanger for thermal regeneration, which turns to be thermodynamically favourable in this range of power output. If a thermal load is required the system operates in CHP configuration and part, or the whole, of turbine exhaust gases are sent to a Heat Recovery Boiler for water heating. The HRB is, in analogy to the Regenerator, a counter flow surface heat exchanger. The mass of hot gases directed to each heat exchanger can be controlled by a regulation valve that allows, for a given fuel mass flow rate, to enhance the net power output or to privilege the thermal generation at the HRB. This degree of freedom allows the system to operate at different cogeneration degrees, thus covering many power-to-heat demand ratios. The whole system is modeled in the Simulink ® environment, a powerful tool for dynamic system analysis. All components are studied and a mathematical representation for each of them is described. Equations are then implemented in Simulink ® allowing to create customized blocks of different components which are then properly coupled, respecting the physical causality of the real system, by connections that may represent either mechanical or fluid dynamic links. Models are classified depending on whether state variables for the considered component can be defined or not. Compressor and turbine are represented as “Black Box” components without state, while the combustion chamber is modelled as a “white box” applying energy and mass conservation equations with three state variables. Heat exchangers are considered as “White Box” without state, and the physics of the heat exchange process is studied according to the Effectiveness-NTU method. A further dynamic equation is the shaft dynamic balance equation. Model results are reported in the paper in several transient conditions: in all cases the computational time proved to be lower than real time.

Over the past several years, customer-sited cogeneration systems have been viewed as a way to mitigate electrical supply shortages. On the utility side, achieving this goal requires cogeneration systems to operate at a relatively high capacity factor, especially during peak periods. On the customer side, the cogeneration system must be capable of reducing operating costs, which can be accomplished by running the system at high operational efficiency and recovering available waste heat. Our firm has been evaluating customer-sited cogeneration systems installed under the Self Generation Incentive Program (SGIP). This paper will present the results of an in-depth performance evaluation conducted for the SGIP Working Group to evaluate the effectiveness of useful thermal energy recovery of on-site cogeneration systems that received incentives from the program. An earlier study investigated levels of energy efficiency and useful waste heat recovery achieved by cogeneration systems in the SGIP. This study raised some interesting questions regarding the actual operational efficiencies of cogeneration systems and low thermal heat recovery. By incorporating fuel consumption, thermal energy recovery and prime mover performance data obtained through the Program’s measurement and evaluation monitoring efforts, actual measured performance was compared to engineering estimates of performance for each project. Thermal heat recovery plays an important role in the overall performance of a cogeneration system. This paper will explore some of the key drivers behind the unexpectedly low thermal energy recovery and overall plant performance. Possible ways to improve the useful waste heat recovery will also be discussed. Regular maintenance and thorough monitoring of the cogeneration system has big impact on the performance. Because the performance data includes the actual timing (hour and month) of cogeneration system operation, the effects of this distributed generation resource is evaluated by taking into account the large differences between peak and offpeak energy costs and benefits. This program-level distributed generation analysis can help program designers and policy makers to understand the limitations of smaller cogeneration applications relative to those systems envisioned under Public Utility Regulatory Policy Act (PURPA) and thus may have important policy implications for the future of cogeneration and distributed generation programs throughout the U.S.

Fuji Electric Group has sold many 100kW phosphoric acid fuel cell (PAFC) generation systems. These PAFC systems have achieved the initial development goal of a cell life of 40,000 hours (approximately 5 years). The first set of second-commercial-type 100kW PAFC (FP-100F) has been operated since December 2001 at a training institute of Fuji Electric Human Resources Development Center Co., Ltd. The facility has introduced a new energy generation system composed with a 100kW PAFC, a 26kW micro gas turbine and a 10kW photovoltaic generation. This new energy generation system aims to save energy with mainly use PAFC for supplying electrical power, and micro gas turbine for heat demand. This system has been achieved to reduce CO 2 emissions of 30%, and to save energy of 13% during December 2001 to March 2004, compared with conventional commercial electric power and a boiler.

A high efficient co-generation system named “Neighboring Communities Co-generation System” is proposed to a multiple dwelling house. The key technology of this system is to connect home and home with one loop of heat transfer line of one-inch diameter, and to level the heat demand by a heat storage unit in each house. This system requires a compact heat storage unit of quick response. In this study, a plate fin type brazing heat exchanger was built and tested as the heat storage unit. Sodium acetate trihydrate with a melting point of about 58 °C and a paraffin wax with a higher value of 74.8 °C were used as the phase change material (PCM). As a result, it was shown that the heat transfer in the heat storage unit was dominated by thermal conductivity in PCM. The paraffin wax showed higher responsibility and higher heat output due to its higher melting point and quite lower super cooling in solidification.

In recent years there has been great deal of effort made in promoting combined heat and power (CHP) and its related economic and environmental benefits. Much of this effort has been targeted at industries because they are generally the best suited to host a CHP system. In spite of the efforts and the assistance available, many industries do not seem overly enthusiastic about installing CHP. The primary reason appears to be that electric rates are low relative to typically used fuels such as natural gas. This translates into a longer return on investment than most companies can justify in the face of competing internal pressures. Trying to encourage industries to install CHP in a struggling economy is just that much more difficult. When CHP is installed, there is usually another motivating factor such as a “free” fuel or concerns about power reliability. Does this mean that CHP is not the great solution everyone has been talking about? The author does not believe so. However, maybe it is time to redefine the application of CHP by simply reconsidering the boundary under which it is typically applied. For example, by considering CHP at a State boundary as opposed to a facility boundary, CHP takes on an entirely new role. Expanded benefits can now include economic development, homeland security, environmental sustainability, improved power transmission and distribution and job creation.

This paper presents the optimal plan in an assumed cogeneration system based on Advanced Co-generation system built in Kikui-cho campus and suggests the introductory technique of co-generation system. At first, we analyzed the annual change of the electric power and cooling demand for a typical consumer and completed the assumed model by formulating. In hospital, hotel, etc., it was checked that electric power and cooling demand have the high correlation with outside temperature, and the daily maximum temperature is effective as an explaining variable especially. We verified the optimal planning according to the consumer using this assumed demand.

The paper will introduce the research community to the Mississippi Micro-CHP (Cooling, Heating, and Power) and Bio-fuel Center, a unique research, demonstration and education center combining the resources and expertise from Mississippi State University Engineering, Agriculture, and the Mississippi Agricultural and Forestry Experiment Station (MAFES). The center is a vertically integrated program to study and demonstrate the entire bio-fuel utilization cycle from “woodchips to micro-CHPs”: feedstock production, conversion to bio-fuel/biogas, conversion to onsite electrical power, and utilization of the resulting waste heat to provide the site’s cooling and heating needs. The “micro” designates a focus on residential, small commercial and rural applications. The coupling of micro-CHP with bio-fuels has to do with addressing regional and demographic consideration of successful micro-CHP implementation as opposed to a one-strategy-fits-all approach. The paper will contrast characteristics of residential and small commercial establishments versus commercial/industrial CHP systems and form a list of desirable characteristics for micro-CHP components and overall micro-CHP system design. Based on these evaluations, future research plans for the Center will be suggested. Another factor that will be stressed is that Micro-CHP will best be utilized if designed as part of a whole building system. The characteristics of the building are as important as the characteristics of the equipment, and both should be designed to work together synergistically.