Multi objective short term hydro-thermal- CHP scheduling using social spider algorithm

The Combined Heat and Power (CHP) concept is aptly suited to improve or eliminate some of the global and local issues concerning electric commercial buildings. CHP involves on-site or near-site generation of electricity by using gas-fired equipment along with utilization of thermal energy available from the power generation process. CHP has the potential of providing a 30% improvement over conventional power plant efficiency and a CO2 emissions reduction of 45% or more. In addition, an overall total system efficiency of 80% can be achieved because of the utilization of thermal energy, that would otherwise be wasted, and the reduction of transmission, distribution and energy conversion losses. CHP technology also makes cost savings possible by reducing high summertime electrical demand charges while at the same time providing necessary space heating and cooling. Savings are further increased in applications where waste heat can replace electric heating. Moreover, CHP has the ability to address indoor air quality issues when utilizing a desiccant dehumidifier by providing direct humidity control and consequently reducing the potential for mold and bacteria development. Because power generation is done on-site, CHP provides control in meeting a building’s electrical needs and also provides an increased level of reliability to ensure high employee productivity. The current research is being carried out in a four–story commercial office building that has been established as the CHP research and demonstration facility on the campus of the University of Maryland in College Park, MD, USA. The 52,700 square feet administrative building includes two heating, ventilating and air-conditioning (HVAC) zones of equal area where zone 1 includes the first and second floors and zone 2 includes the second and third floors. This has facilitated the installation of two different CHP systems for the two zones. The research in this paper discusses about the CHP system catering to zone 1. This paper describes a second generation CHP system involving the integration of a new 75 kW commercial engine generator with the existing liquid desiccant system. The engine generator is connected parallel to the grid for supplying 75 kW of electrical power to the building while the combined waste heat recovered from the exhaust gases as well as the jacket water from the engine is used to heat a 50:50 ethyl glycol–water loop through a packaged heat recovery system. This recovered heat is then used for the regeneration of the lithium chloride solution in a liquid desiccant system and the ethyl glycol–water solution is returned back to the engine. The liquid desiccant system reduces the latent load of the ventilation air entering the roof top unit. Technical challenges concerning electrical and control aspects that were related to modifications of the original CHP system are described and improvements to the original system design and performance are evaluated. The paper then discusses the experimental results obtained with first generation CHP system and its overall performance.

Combined heat and power (CHP) is the fuel unbiased method of production of heat energy and electrical power. Increased efficiency to the tune of 80% and above and reduced emission are two key attributes of this method as the production is obtained in a single process. This dissertation considered prohibited operating zones (POZ) and valve point effect (VPE) of generators in the study of Static Optimal load flow of CHP with the objective to reduce production cost while voltage level of buses are maintained within specified limit in order to satisfy the electrical power and heat demands. Optimization of load flow through such a power system is done using bio-inspired Social Spider algorithm. The distance of spider from food is defined as objective function. Two test systems having six generators in each have been used in IEEE 30 bus framework to demonstrate the efficacy of this algorithm. Results show that this method is competent enough to solve problem of multi objective optimization.

Economic output-maximizing share of combined heat and power generation: The case of South Korea

Malaysia is presently the world’s largest exporter of palm oil with total production of 19.22 million tonnes of crude palm oil (CPO) in 2013. Aside CPO, by-products such as empty fruit bunch (EFB), palm kernel shell (PKS), palm kernel oil (PKO), palm kernel cake (PKC) and pressed palm fibres (PPF) are produced from the palm oil mills. These biomasses can be used as potential feedstock for the production of biofuels, biogas and bioelectricity. One of the ways to fully harness the potentials of these biomasses is by employing the biorefinery concepts where all the products and by-products from oil palm are utilized for production of valuable bio-products. In this study, technological feasibility of biorefinery for the production of biodiesel, hydrogen, Fischer-Tropsch liquids (FTLs) integrated with combined heat and power (CHP) generation was investigated. Flowsheet was designed for each of the processes using Aspen HYSYS® v 8.0. Material balance was performed on a palm oil mill processing 250 tonnes per year of fresh fruit palm (FFP). Results from the material balance shows that 45.1 tonnes of refined bleached deodorized palm oil (RDBPO) and 52.4 tonnes of EFB were available for the production of biodiesel, hydrogen, FTLs and the CHP generation. The annual plant capacity of the biodiesel production is estimated to be 26,331.912 tonnes. The overall energy consumption of the whole process was estimated to be 36.0 GJ/h. This energy demand was met with power generated from the CHP which is 792 GJ/h leaving a surplus of 756 GJ/h that can be sold to the grid. The process modelling and simulation of the biorefinery process shows technological feasibility of producing valuable products from oil palm.

Covariance matrix adaptation evolution strategy with directed target to best perturbation (CMS-ES_DTBP) scheme is applied for determining the optimal hourly schedule of power generation in a hydro-thermal power system. In the proposed approach, a multi-reservoir cascaded hydro-electric system with a nonlinear relationship between water discharge rate, net head and power generation is considered. Constraints such as power balance, water balance, reservoir volume limits and operation limits of hydro and thermal plants are also considered. The feasibility, and effectiveness of the proposed algorithm is demonstrated through a test system, and the obtained results are compared with the existing conventional and evolutionary algorithms. Simulation results reveal that the proposed CMS-ES_DTBP scheme appears to be best in terms of convergence speed and cost compared with other techniques.

This paper presents the solution to the combined heat and power economic dispatch problem using a direct solution algorithm for constrained optimization problems. With the potential of Combined Heat and Power (CHP) production to increase the efficiency of power and heat generation simultaneously having been researched and established, the increasing penetration of CHP systems, and determination of economic dispatch of power and heat assumes higher relevance. The Combined Heat and Power Economic Dispatch (CHPED) problem is a demanding optimization problem as both constraints and objective functions can be non-linear and non-convex. This paper presents an explicit formula developed for computing the system-wide incremental costs corresponding with optimal dispatch. The circumvention of the use of iterative search schemes for this crucial step is the innovation inherent in the proposed dispatch procedure. The feasible operating region of the CHP unit three is taken into account in the proposed CHPED problem model, whereas the optimal dispatch of power/heat outputs of CHP unit is determined using the direct Lagrange multiplier solution algorithm. The proposed algorithm is applied to a test system with four units and results are provided.

Combined heat and power (CHP) has been identified by the Second and Third Assessment Report of the Intergovernmental Panel on Climate Change as a powerful carbon abating technology. In this paper, we review trends and overall changes in power generation technologies insofar as these affect industrial CHP in Japan; we also propose an empirical model for the analysis of CHP adoption based on time series cross-sectional (panel) data. This is followed by a discussion on current energy policy targets towards CHP and the changes in steam capacity (process heat) that have occurred during the period 1985-1998. Site information on 1500 CHP sites was gathered and combined with industrial statistics for a 14 year span during which Japanese power markets underwent deregulation. Based on the panel regression, we found that an increase in the probabilities of installing new CHP will be linked with a unit increase in purchased power, industrial production and consumption of self-generated power, while a unit increase in non-CHP boiler steam capacity will decrease the probability of adding CHP for the 7 industries. The fixed effects model showed that CHP faces increasing returns to scale over the period 1985-1998. Empirical work on CHP on cross sectional studies carried elsewhere confirms some of our findings. Additionally, it is found that adoptions of CHP are linked to the small to medium size industrial plants since the latter account for the mass of steam capacity retired.

This work aims to assess the effect of the operating parameters of the gasifying agent preheating temperature and equivalence ratio (ER) on the conversion of sewage sludge (SS) to syngas through gasification and combined heat and power (CHP) generation. A novel gasification model was simulated in Aspen Plus to represent a fixed-bed updraft gasifier to generate syngas from SS through an equilibrium approach restricted by temperature. The novelty of this work is that the model was developed by applying the gasifying agent preheating temperature as an operating variable instead of the gasification temperature. It was calibrated by using a set of experimental values and then validated by comparing the numerical results with the experimental outcomes related to nine different operating conditions of air preheating temperatures and ER. A good agreement between the simulation and experimental results was observed. The optimum gasification process parameters of the air preheating temperature and ER were predicted to be 150 °C and 0.2, respectively. The CHP generation potentiality of SS was assessed to be 2.54 kW/kg SS as dry solids (DS), of which 0.81 kW was electrical and the remainder was thermal power. The conversion of SS to CHP through the proposed treatment can reduce 0.59 kg CO₂/kg SS as DS emissions compared with that of natural gas combustion to generate a similar quantity of energy.

Techno-economic evaluation of medium scale power to hydrogen to combined heat and power generation systems

Policy instruments clearly influence the choice of production technologies and fuels in large energy systems, including district heating networks. Current Swedish policy instruments aim at promoting the use of biofuel in district heating systems, and at promoting electric power generation from renewable energy sources. However, there is increasing pressure to harmonize energy policy instruments within the EU. In addition, natural gas based combined cycle technology has emerged as the technology of choice in the power generation sector in the EU. This study aims at exploring the role of policy instruments for promoting the use of low CO2 emissions fuels in high performance combined heat and power systems in the district heating sector. The paper presents the results of a case study for a Swedish district heating network where new large size natural gas combined cycle (NGCC) combined heat and power (CHP) is being built. Given the aim of current Swedish energy policy, it is assumed that it could be of interest in the future to integrate a biofuel gasifier to the CHP plant and co-fire the gasified biofuel in the gas turbine unit, thereby reducing usage of fossil fuel. The goals of the study are to evaluate which policy instruments promote construction of the planned NGCC CHP unit, the technical performance of an integrated biofuelled pressurized gasifier with or without dryer on plant site, and which combination of policy instruments promote integration of a biofuel gasifier to the planned CHP unit. The power plant simulation program GateCycle was used for plant performance evaluation. The results show that current Swedish energy policy instruments favour investing in the NGCC CHP unit. The corresponding cost of electricity (COE) from the NGCC CHP unit is estimated at 253 SEK MWh−1, which is lower than the reference power price of 284 SEK MWh−1. Investing in the NGCC CHP unit is also shown to be attractive if a CO2 trading system is implemented. If the value of tradable emission permits (TEP) in such as system is 250 SEK tonne−1, COE is 353 SEK MWh−1 compared to the reference power price of 384 SEK MWh−1. It is possible to integrate a pressurized biofuel gasifier to the NGCC CHP plant without any major re-design of the combined cycle provided that the maximum degree of co-firing is limited to 27–38% (energy basis) product gas, depending on the design of the gasifier system. There are many parameters that affect the economic performance of an integrated biofuel gasifier for product gas co-firing of a NGCC CHP plant. The premium value of the co-generated renewable electricity and the value of TEPs are very important parameters. Assuming a future CO2 trading system with a TEP value of 250 SEK tonne−1 and a premium value of renewable electricity of 200 SEK MWh−1 COE from a CHP plant with an integrated biofuelled gasifier could be 336 SEK MWh−1, which is lower than both the reference market electric power price and COE for the plant operating on natural gas alone. Copyright © 2005 John Wiley & Sons, Ltd.

Customer-side electricity load management for sustainable manufacturing systems utilizing combined heat and power generation system

A social spider algorithm for solving the non-convex economic load dispatch problem

Advanced control of large-scale wind turbines: Structural load reduction and lifetime control

A study on the optimum arrangement of prime movers in small scale microturbine-based CHP systems

Microgrids have become attractive electricity supply and management options that support local power generation, increased reliability, sustainability, and cost reductions. Microgrid sources often include solar PV, wind, and a thermal generation. Thermal generation alone has low conversion efficiency. On the other hand, a combined heat and power (CHP) generator provides additional benefits by taking advantage of the exhaust heat from the generator to fulfill the thermal demand of a building. Thus an integrated microgrid that includes renewable energy and a CHP unit to serve electrical and thermal loads of buildings can achieve higher overall efficiency. In this paper, we model a thermal and electrical energy microgrid, which accounts for the nonlinear efficiency of a Capstone CHP unit and the thermal dynamics of a building. We present the steady-state model as well as the optimization scheduling formulation to minimize the integrated operating cost of the microgrids. The model is simulated under three electricity pricing structures to gain insight into the impacts of pricing on the daily operation of the microgrid.