A review is presented on the technology, thermodynamics, applications and economics of absorption cycles such as refrigeration, heat pumps and temperature amplifiers; single and multistage cycles, and systems into which they are integrated such asCHP. From this present situation the fundamental thermodynamics of ideal absorption refrigeration is established for single, double and multistage cycles. An exergy analysis is used to prove this theory. The ideal absorption cycle theory is developed to cover absorption heat pumps, cooling with heat recovery, temperature amplifiers and hybrid systems incorporating vapour compression and absorption machines. Having proved absorption cycles to be comprised of Carnot cycles (direct and reverse), this theory was then merged with Carnot driving and cooling cycles' theory to establish a universal law of cold generation cycles. These are combinations of driving and cooling cycles for which the main pmpose is to produce cooling from a combustion driven cycle. The applications and economic evaluations of real direct fired absorption chillers, cold generation systems and the application of absorption chillers to combined heat and power (CHP) systems are analysed. Direct fired chillers have been proved to be economically feasible. The analysis of cold generation cycles indicated the feasibility of certain plant configurations. For the CHP analysis, the exergy costing method was seen to be the most appropriate one for determining the most cost effective application. A review of thermoeconomics applied to an air conditioning system with absorption and CHP is presented. Thermoeconomics was shown to be an appropriate method for optimising systems where absorption cycles are applied. Finally theoretical, practical and economic conclusions are presented regarding the equivalence of vapour compression and absorption cycles.

The purpose of this project was to optimise a diesel engine converted to operate on natural gas, to suit the requirements for: low emissions, a high efficiency and sufficient power delivery within the constraints of cogeneration (combined heat and power) systems. Cogeneration Installations seek to improve the efficiency of power generation by utilising waste heat from the prime mover, as well as the production of electricity. Many small scale systems are based on open chamber gas engines, and, to reduce the payback time for the installation, the overall engine efficiency is of prime importance. Stationary engines can be subject to strict standards for emissions, the greatest challenge being presented by the control of NO emissions. The main difficulty is that the highest efficiency operating point of a spark ignition engine is also the point of maximum NO emissions. The extent of this problem was analysed by conducting tests across the entire operating map of the baseline engine at the required speed of 1500 rpm. The solution, in the form of a new high compression ratio combustion system was based on the following: An extensive literature review, the previous Brunel experience with gas engines, an evaluation of the baseline combustion and emissions performance, and the predictions of the Integrated Spark Ignition engine Simulation (ISIS) thermodynamic model. Tests were conducted on the new Fast Bum High Compression Ratio combustion system at compression ratios of 15:1 and 13:1, which demonstrated an extended lean burn capability such that an operating point was identified, that satisfied the conflicting requirements of: low emissions (less than 1g NOx/kWh or 360mg/m3), and a high brake efficiency (above 30%), as well as particular cogeneration criteria. The bmep was mostly above 6 bar. After further tuning and calibration with experimental data, the ISIS model was used to predict the engine power output, efficiency and emissions (NOx and CO) for the compression ratio of 15:1, across the entire operating map for both naturally aspirated and turbocharged configurations. The naturally aspirated results showed good agreement with the results of the experimental 15:1 FBHCR combustion system. The turbocharged engine was simulated with a bmep of 10 bar. The results identified much larger operating areas and all emissions limits were met above a brake efficiency of 36%. The conclusions are, that an open chamber fast bum high compression ratio combustion system can achieve very low emissions, particularly of NOx, and a high efficiency by having the capability of operating with lean enough mixtures. Further improvement in the efficiency is likely if other engine parameters (such as the valve timing) were to be optimised for 1500 rpm. The results from the turbocharged simulation show that turbocharging, whilst restoring the output can also achieve low emissions, and a higher efficiency than a naturally aspirated engine.

The research in this thesis has undertaken a technical, economic and environmental appraisal of three gas-fired, small-scale Combined Heat-and-Power (CHP) systems together with a study of the UK's electricity supply industry (ESI) and CHP market. The purpose of each system is to attempt to utilise more of the heat and/or electricity output from the CHP unit. Within the non-technical research area, three scenarios for the evolution of the ESI have been developed to help establish how changes to forces acting within the industry might affect the development of the UK CHP market. New applications of several strategic management analysis tools were used to develop and select the following scenarios: (i) New and reduced CO₂ limits set by the Climate Control Conference + stricter environmental legislation; (ii) Changes to the Pool mechanism for pricing electricity; (iii) Business as usual. It was concluded that in isolation scenarios 1 and 3 would aid the expansion of the CHP market, whereas scenario 2 is likely to hinder it. The selection of the scenarios and the implications for the ESI and CHP market are supported by the opinions of 'industry specialists', which were solicited in a survey specifically undertaken for this study. The investigation into the first of the three technical systems involves the substitution of two separate CHP units in place of a single larger unit. The intention is to operate the larger of the two CHP units at maximum output to satisfy the base heat-load and to use the second unit for meeting peak loads. The results for five test-cases were produced via a newly-developed predictive model, and indicated that it is possible, for one of the case studies considered, to achieve shorter pay-back periods when using the double-unit - with a higher availability of 95% - rather than the single-unit system. In the other two cases (where CHP is a viable economic option), longer pay-back periods ensue by the installation of the two unit rather than the single-unit system. The operation of the two-unit system can potentially increase energy-utilisation from the CHP units at one of the other sites. Furthermore, the proposed system can offer, in some cases, significant secondary benefits, which could encourage a potential investor in the technology. These benefits include the increased heat-and-electricity output, increased availability from the system, back-up from the secondary unit if one unit fails. The second system determines the viability of an integrated small-scale CHP and TES system. Another predictive model was developed and tested on five test-cases. It was found that there is insufficient potential for the system and that the potential is limited by the following factors: (i) CHP-sizing methodology, (ii) the relatively high capital cost for TES hardware and installation, (iii) the relatively low economic value attributed to heat and (iv) the availability of low-priced off-peak electricity. An industrial case study provided a rare and useful operational example of the proposed system and the findings indicated that the heat-store could reduce the energy and monetary expenditures by up to 2.8% of the site's annual gas usage, displacing approximately 30 tones Of CO₂ emissions each year. However, because of the high financial cost of the TES components and installation, the pay-back period produced would rarely be acceptable to a prospective investor, except in exceptional circumstances. Finally, the viability of an integrated CHP/absorption chiller system was investigated. The effectiveness of these types of systems are dependent on several factors, namely: the source-water temperature from the hot-engine CHP unit - for a high COP - and the cooling load at the site, the cooling demand at the site and the temperature of the cooling water. A first-stage predictive model was developed to determine the initial appropriateness of the installation of the integrated system at a local hospital for the first time. The indications were that the cooling demand was too low and the surplus waste-heat from the CHP unit insufficient to make the system viable at the site. A second working-system was studied with a full CO₂ investigation undertaken. The intention was to compare the total CO₂ emissions for the integrated CHP and absorption chiller system with those for a similarly sized vapour-compression system. The results indicate that the installed system will produce 0.30kg CO₂/kWhcoolth compared with 0.27 kg and 0.32kg for two different types of vapour compression systems at design conditions. If the CHP heat output is increased - to supply all of the heat required by the absorption chiller - then the proposed system can displace up to 0.06 kg CO₂ per kWhcoolth at design conditions and 0.10 kg CO₂ per kWh of cooling delivered for lower cooling water temperatures. This represents a reduction of 22% and 40% respectively, when compared with the vapour-compressions system.

No description available.

In this research, a new combined heat and power (CHP) system configuration has been proposed that uses two power generation units (PGU) operating simultaneously with different operational strategies (D-CHP). The performance of the proposed D-CHP system configuration, with one PGU operated at a constant base load and the other operated following the electric load, is quantified in terms of operational cost savings, primary energy consumption (PEC) savings, and carbon dioxide emissions (CDE) savings over a reference case employing a conventional, separate heat and power system. D-CHP system performance is also compared to standard, single PGU operational strategies. The D-CHP system configuration is first examined for four different building configurations simulated using the weather of Chicago, IL. Then, the D-CHP system feasibility study is extended to examine a full-service restaurant benchmark building in nine different U.S. climate zones. Next, the D-CHP configuration is simulated under a second operational strategy, in which one PGU operates base-loaded while the other follows the thermal load, and the two D-CHP strategies are compared. Additionally, the effect of thermal storage on D-CHP system performance is examined. Finally, the D-CHP configuration is extended to a combined cooling, heating, and power configuration (D-CCHP), and the feasibility of this configuration is examined. In addition to D-CHP and D-CCHP systems performance analyses, the parameters of power-to-heat ratio; cost, emissions and primary energy consumption spark spreads; cost and emission ratios; and thermal difference are proposed and examined as performance indicators. It was determined that D-CHP and D-CCHP system strategies can be a viable alternative to traditional CHP system or combined cooling, heating, and power (CCHP) system operational strategies, in terms of operational cost, PEC, and CDE performance. Generally, the D-CHP and D-CCHP configurations are found to perform comparably to or better than traditional CHP and CCHP configurations.

This thesis evaluates the effects of Combined Heating and Power (CHP) systems with a Propane fueled spark ignited engine as prime mover used in a small commercial building. The system was evaluated in five different U.S. cities. The most common operating modes, thermal load following (FTL) and electric load following (FEL) were evaluated, and an optimized operating mode was developed and investigated. The optimized operating mode is a hybrid (FHL) of FEL and FTL operation. Methodology for the derivation and application of these models is presented. Also, the economic effects of Diesel and Natural Gas were investigated. The results for all five cities and all three operating modes were gathered and compared with a conventional system. Comparisons were made based on cost, primary energy consumption, and carbon dioxide emissions. It was concluded that the feasibility of CHP had great potential, but is highly dependent upon the location of the system.

No description available.

Commercial Buildings and complexes are no longer just national heat and power network energy loads, but they are becoming part of a smarter grid by including their own dedicated local heat and power generation. They do this by utilising both heat and power networks/micro-grids. A building integrated approach of Combined Heat and Power (CHP) generation with photovoltaic power generation (PV) abbreviated as CHPV is emerging as a complementary energy supply solution to conventional (i.e. national grid based) gas and electricity grid supplies in the design of sustainable commercial buildings and communities. The merits for the building user/owner of this approach are: to reduce life time energy running costs; reduce carbon emissions to contribute to UK’s 2020/2030 climate change targets; and provide a more flexible and controllable local energy system to act as a dynamic supply and/or load to the central grid infrastructure. The energy efficiency and carbon dioxide (CO2) reductions achievable by CHP systems are well documented. The merits claimed by these solutions are predicated on the ability of these systems being able to satisfy: perfect matching of heat and power supply and demand; ability at all times to maintain high quality power supply; and to be able to operate with these constraints in a highly dynamic and unpredictable heat and power demand situation. Any circumstance resulting in failure to guarantee power quality or matching of supply and demand will result in a degradation of the achievable energy efficiency and CO2 reduction. CHP based local energy systems cannot rely on large scale diversity of demand to create a relatively easy approach to supply and demand matching (i.e. as in the case of large centralised power grid infrastructures). The diversity of demand in a local energy system is both much greater than the centralised system and is also specific to the local system. It is therefore essential that these systems have robust and high performance control systems to ensure supply and demand matching and high power quality can be achieved at all times. Ideally this same control system should be able to make best use of local energy system energy storage to enable it to be used as a flexible, highly responsive energy supply and/or demand for the centralised infrastructure. In this thesis, a comprehensive literature survey has identified that there is no scientific and rigorous method to assess the controllability or the design of control systems for these local energy systems. Thus, the main challenge of the work described in this thesis is that of a controller design method and modelling approach for CHP based local energy systems. Specifically, the main research challenge for the controller design and modelling methodology was to provide an accurate and stable system performance to deliver a reliable tracking of power drawn/supplied to the centralised infrastructure whilst tracking the require thermal comfort in the local energy systems buildings. In the thesis, the CHPV system has been used as a case study. A CHPV based solution provides all the benefits of CHP combined with the near zero carbon building/local network integrated PV power generation. CHPV needs to be designed to provide energy for the local buildings’ heating, dynamic ventilating system and air-conditioning (HVAC) facilities as well as all electrical power demands. The thesis also presents in addition to the controller design and modelling methodology a novel CHPV system design topology for robust, reliable and high-performance control of building temperatures and energy supply from the local energy system. The advanced control system solution aims to achieve desired building temperatures using thermostatic control whilst simultaneously tracking a specified national grid power demand profile. The theory is innovative as it provides a stability criterion as well as guarantees to track a specified dynamic grid connection demand profile. This research also presents: design a dynamic MATLAB simulation model for a 5-building zone commercial building to show the efficacy of the novel control strategy in terms of: delivering accurate thermal comfort and power supply; reducing the amount of CO2 emissions by the entire energy system; reducing running costs verses national rid/conventional approaches. The model was developed by inspecting the functional needs of 3 local energy system case studies which are also described in the thesis. The CHPV system is combined with supplementary gas boiler for additional heating to guarantee simultaneous tracking of all the zones thermal comfort requirements whilst simultaneously tracking a specified national grid power demand using a Photovoltaics array to supply the system with renewable energy to reduce amount of CO2 emission. The local energy system in this research can operate in any of three modes (Exporting, Importing, Island). The emphasise of the thesis modelling method has been verified to be applicable to a wide range of case studies described in the thesis chapter 3. This modelling framework is the platform for creating a generic controlled design methodology that can be applied to all these case studies and beyond, including Local Energy System (LES) in hotter climates that require a cooling network using absorption chillers. In the thesis in chapter 4 this controller design methodology using the modelling framework is applied to just one case study of Copperas Hill. Local energy systems face two types of challenges: technical and nontechnical (such as energy economics and legislation). This thesis concentrates solely on the main technical challenges of a local energy system that has been identified as a gap in knowledge in the literature survey. The gap identified is the need for a controller design methodology to allow high performance and safe integration of the local energy system with the national grid infrastructure and locally installed renewables. This integration requires the system to be able to operate at high performance and safely in all different modes of operation and manage effectively the multi-vector energy supply system (e.g. simultaneous supply of heat and power from a single system).

District heating systems can contribute to reducing the UK's CO2 emissions. This thesis investigates the operational performance of current district heating (DH) systems with the existing and a possible future energy sector. The main contributions to knowledge are:  Operational, financial and exergy performance assessments of three functioning DH systems and one decentralised energy (DE) technology  A methodology to optimise a DH system in a resource efficient and cost effective way The aims of DH systems are to provide heat, reduce CO2 emissions, ensure energy security by operating in a resource efficient way and to tackle fuel poverty. However, the case studies in this project confirm that DH systems operate poorly in the UK. This is largely because of the heat losses from the DH network to the soil being high and the plant operation being suboptimal. Four case studies were analysed. The 785 room Strand Palace hotel has two 250 kWe combined heat and power (CHP) engines set to modulate following the hotel's electricity consumption and providing approximately 90% of this annual demand. It was found that the CHP engines never operate at full load throughout a full day, firstly because the plant cannot export electricity to the grid and secondly the system is not fitted with a thermal store. Financial analysis revealed that the hotel does not reduce its heating cost by operating the CHP engines, but that the energy service company (ESCo) makes £77,000 net operating income per year. Elmswell in Suffolk (UK) is a low heat density DH system that generates heat with a 2008 biomass boiler and pumps it to 26 terraced and semi-detached dwellings. It was found that 39% of its heat is lost to the soil and that the natural gas boiler generates 45% of the heating load and operates with a seasonal efficiency of 65%. The heat losses to the soil for this system were compared to a DH system of higher heat density, Loughborough University, with a lower heat loss of 22% to the soil. In August 2011, Loughborough University installed a 1.6 MWe CHP engine to operate with four 3 MWth natural gas boilers to supply heat to its DH network. A study undertaken demonstrated that by adding a 2 MWe CHP engine with a thermal storage instead of a 1.6 MWe CHP engine on its own could further increase the CO2 emissions savings from 8% to 12.4%. The energy centre at Pimlico District Heating Undertaking (PDHU) includes a gas fired cogeneration plant that supplies heat to 3 schools, 3,256 dwellings and 55 commercial units. It also benefits from a 2,500 m3 thermal store. Every component of PDHU was investigated in detail and its current operation was optimised and compared to a selection of new operating scenarios. It was found that: i) The thermal store operated with 93% thermal efficiency and was not used to reduce the energy consumption or to enable more cogeneration, ii) The CHP engines were undersized and generated only 18% of the required heat in 2012, iii) The boilers modulate and £ 70,000 could be saved per year by setting them to operate at full load by making use of the thermal store, iv) By installing an open-loop heat pump using the river Thames, PDHU could then guarantee to comply with current and likely future policies impacts by setting the energy plant to operate in CHP mode or as an electricity consumer at defined times to benefit from low energy utility costs and to minimise CO2 emissions. A comparison of selected performance metrics was then undertaken and it was found that none of the three DH systems operate in a resource efficient way and that the heating cost could be reduced further by optimising the operation of the systems. To do this, a new optimisation methodology is proposed by maximising their exergy efficiency in addition to maximising their overall energy efficiency and CO2 emissions reduction.

Today’s biomass-fired combined heat and power (CHP) plants have surplus heat production capacity during warmer times of the year. In order to allow them to increase their electricity production, it is essential to find a use for the surplus heat. Additionally, the transport sector is struggling with high fuel prices and the contribution of CO2 emissions to global warming. A promising way of reducing the negative effects caused by combustion of fossil fuels in the transport sector is to mix ethanol with gasoline, or to use pure ethanol in modified engines. Ethanol is produced by fermentation at low temperatures and the production process could be integrated with CHP plants. The first generation of ethanol production as fuel has recently been criticized for competing with food crops and for its production chain being a larger polluter than was first thought. The second generation of ethanol production from lignocellulosic materials offers very promising results, but this process has several steps that are energy demanding. This thesis presents the findings of research on the configuration of a CHP plant with an integrated second generation ethanol production process. It also presents the operational economics and optimal locations for such plants in Sweden. Two case studies were performed to compare different feedstocks for ethanol production. The results show that when electricity prices are high, CHP plants benefit from heat consumption. Even with low yields in an ethanol production process, the integrated plant can be profitable. The plant must be located where there is sufficient heat demand. A cellulosic ethanol production process can work as a heat sink with profitable outcomes even with the current state of development of cellulosic ethanol technology.