Publications
34 results found
Patel DN, Matalon P, Oluleye G, 2024, A novel temporal mixed-integer market penetration model for cost-effective uptake of electric boilers in the UK chemical industry, Journal of Cleaner Production, Vol: 446, ISSN: 0959-6526
The UK chemical industry is the largest consumer of natural gas for process heating and power generation, with an annual consumption of 26.3 TWh. Reduction in natural gas consumption and associated carbon emissions can be achieved through electrification of heat. However, the adoption of electric boilers is lethargic due to economic barriers. Hence, market-based policy interventions are required. This study aims to accelerate the adoption of electric boilers in the UK's chemical industry, aligning with the UK's ambitious 2035 industrial decarbonisation goals while considering economic impacts, by designing market-based policy interventions and comparing two adoption patterns. A novel multi-period Mixed-Integer Market Penetration Optimisation Model is developed and applied to inform decisions about transitioning from natural gas to electric boilers. The model is applied to a case study of all the heating systems (490 boilers) in the UK chemical industry from 1 MW to 60 MW boilers. Results show that effectively implementing a gas tax, electricity subsidy, annual grant and carbon tax can generate sufficient demand-pull to reduce the cost of electric boilers from 30 to 85 % depending on the boiler size. A carbon tax starting at £280 per tCO2e and reducing to £170 per tCO2e coupled with electricity subsidies is essential for this transition. The policies are designed such that a win-win is achieved between government and industry; specifically, revenue from the carbon tax and gas tax is used to support the grant and electricity subsidy thereby achieving cost neutrality for government. At 100 % uptake of electric boilers in 2033, the total carbon emissions reduce by 89 %, which is above the 2035 UK industry goal of 60 % reduction. The research establishes a robust policy timeline that can drive industrial electrification in the UK's chemical sector. It highlights the need for a multi-faceted approach, incorporating various policy instruments to overcome the ba
Dalder J, Oluleye G, Cannone C, et al., 2024, Modelling Policy Pathways to Maximise Renewable Energy Growth and Investment in the Democratic Republic of the Congo Using OSeMOSYS (Open Source Energy Modelling System), Energies, Vol: 17
This study sought to generate, evaluate, and recommend possible national policies for the government of the Democratic Republic of the Congo (DRC) to implement to most effectively boost growth and investment in renewable energy technologies (RETs) through 2065 using Open Source Energy Modelling System (OSeMOSYS). The novelty of this study stems in-part from the scarcity of RET modelling completed for specific West African countries rather than for broader regions. Market-based instruments were identified as the policy type most practical for DRC. From modelling the resulting energy systems for policy pathways involving a 16% RET subsidy, a 70% fossil fuel tax, and both in combination relative to no-policy baseline scenarios, the scenarios including the tax had the lowest net costs (USD304–306 B) and the highest proportion of RETs (above 90%). Additionally, despite the current reliance on hydropower to fulfil 98% of its energy needs, hydropower played a very minor role in all of a modelled scenarios (no future investment beyond residual capacity). Finally, a post-modelling market potential assessment was performed on the technology that dominated off-grid supply across policy pathways: a 0.3 kW small solar home system (SHS). Based on learning rates for solar photovoltaics (PV), demand for a small SHS in DRC (>160 million units in total) was found to be sufficient to substantially reduce the unit cost as deployment scales. Ultimately, this study yielded four recommendations for the DRC government: (1) Pursue financial incentives to catalyse DRC’s renewable energy supply. (2) Tax fossil fuel energy production. (3) Re-evaluate focus on hydropower. (4) Promote DRC as a healthy market for solar home systems.
Paiboonsin P, Oluleye G, Howells M, et al., 2024, Pathways to Clean Energy Transition in Indonesia’s Electricity Sector with Open-Source Energy Modelling System Modelling (OSeMOSYS), Energies, Vol: 17
Responding to the Paris Agreement and climate change mitigation, Indonesia aims to reach net zero by 2060 or sooner. Due to Indonesia’s dependence on coal and growing consumption, alternative sources of clean energy are imperative for meeting its rising energy needs and reducing energy-related greenhouse gas emissions to achieve the energy transition. This project aims to examine Indonesia’s opportunities and potential to achieve low carbon ambition in the energy sector and identify alternative pathways for the energy transition in Indonesia. In this study, the open-source energy modelling system (OSeMOSYS), which is a long-term energy system modelling tool, is employed to compare electricity generation, investment, and carbon dioxide emissions between business-as-usual and five alternative scenarios. Six scenarios, including business as usual, least-cost, two coal-phrase out and two net zero aligned with national climate targets and optimal scenarios, were simulated across different target years. The results show that the net zero (NZ) scenario is more cost-effective and emits fewer greenhouse gases than the other scenarios in meeting Indonesia’s future energy demand. However, achieving net zero by 2050 (NZ50) results in significantly lower CO2 emissions (10,134 MtCO2), which is less than half of the emissions in the net zero by 2060 (NZ60) scenario (16,849 MtCO2) at a similar cost (6229 and 6177 billion USD, respectively). This paper’s insights emphasise that large-scale renewable energy deployment and coal retirement are critical pathways to reaching carbon neutrality and achieving the energy mix transition.
Oluleye O, Bishay D, Kas B, 2023, Can a hierarchical ordering of alternative technological concepts for decarbonizing industrial energy systems minimize mitigation costs?, Frontiers in Sustainability, Vol: 4, Pages: 1-15, ISSN: 2673-4524
Integration of alternative technological concepts such as switching to alternative fuels, advanced energy efficiency, and carbon capture & storage in existing industrial energy systems can prove highly effective at minimising emissions; however, their adoption is low since solutions using these concepts raise costs considerably. The hypothesis of this work is a hierarchical combination of these concepts can reduce mitigation cost. To this end a mixed method approach is applied combining energy simulation with a novel Mixed Integer Linear Programming model developed to explore 48 alternative solutions to make industrial energy systems more sustainable. The method was applied to the most common industrial energy systems configurations. Results show that the added cost of integrating alternative technological concepts are lowered when energy efficiency via direct heat recovery is explored first in an optimisation-based hierarchy of options. The hierarchy is advanced energy efficiency before fuel and technology switching or integrating carbon capture and storage. This means process integration can pay for steeper reductions in carbon emissions. Integrating alternative technological concepts optimally and hierarchically reduced emissions by 61%, and costs by 55.7% compared to a partial integration for a heat-only business-as-usual industrial energy systems. Even though switching to an alternative fuel (blue hydrogen) reduces carbon emissions by 72%, costs increase by at least 3% compared to a system using fuel gas and fuel oil. A hierarchical integration of blue hydrogen reduces cost by 47% and carbon emissions by 88.7%. Partial integration of carbon capture and storage reduces carbon emissions by 36% but costs increase by 89%, with full integration using optimisation and the hierarchy costs only increase by 6.3%. therefore, the cost-effectiveness of integrating alternative technological concepts is highly influenced by the hierarchy which seeks to minimise demand fo
Rai U, Oluleye G, Hawkes A, 2022, An optimisation model to determine the capacity of a distributed energy resource to contract with a balancing services aggregator, Applied Energy, Vol: 306, Pages: 1-22, ISSN: 0306-2619
Electricity systems require a real-time balance between generation and demand for electricity. In the past, changing the output of larger generators has been the primary means of achieving this balance, but more recently, smaller distributed energy resources (DERs) are becoming a contributor. As electricity generation becomes more intermittent due to the uptake of renewables, the task of balancing the electricity system is becoming more challenging. As such, there will be a greater need for DERs for grid balancing in future. DERs may be delivered via aggregators for this purpose, where several individual resources are grouped to be traded in contracts with a System Operator (SO). This paper presents a novel framework for DERs aggregators to determine by optimisation the capacity of a generating unit to contract with the SO, using mixed integer non-linear programming (MINLP). Results show the site revenue increases between 6.2% and 29.8% compared to the heuristic approach previously employed. Sensitivity analysis is performed to assess the impact of temporal resolution of demand characterisation on results, showing that increased resolution improves accuracy significantly, and reduces the estimate of capacity that the site should contract with the aggregator.
Sechi S, Giarola S, Lanzini A, et al., 2021, A bottom-up appraisal of the technically installable capacity ofbiogas-based solid oxide fuel cells for self power generation in wastewatertreatment plants, Journal of Environmental Management, Vol: 279, Pages: 1-15, ISSN: 0301-4797
This paper proposes a bottom-up method to estimate the technical capacity of solid oxide fuel cells to be installed in wastewater treatment plants and valorise the biogas obtained from the sludge through an efficient conversion into electricity and heat. The methodology uses stochastic optimisation on 200 biogas profile scenarios generated from industrial data and envisages a Pareto approach for an a posteriori assessment of the optimal number of generation unit for the most representative plant configuration sizes. The method ensures that the dominant role of biogas fluctuation is included in the market potential and guarantees that the utilization factor of the modules remains higher than 70% to justify the investment costs. Results show that the market potential for solid oxide fuel cells across Europe would lead up to 1,300 MW of installed electric capacity in the niche market of wastewater treatment and could initiate a capital and fixed costs reduction which could make the technology comparable with alternative combined heat and power solutions.
Oluleye G, Gandiglio M, Santarelli M, et al., 2021, Pathways to commercialisation of biogas fuelled solid oxide fuel cells in European wastewater treatment plants, Applied Energy, Vol: 282, ISSN: 0306-2619
Fuel cell developments are driven by the need for more efficient and cleaner energy provision; however, current costs make it uneconomic in wastewater treatment plants. Interventions via policy instruments and business models may be required for cost reduction until the fuel cell is driven purely by market forces. In this work a novel market potential assessment methodology is developed and applied to quantify the impact of various interventions on biogas fuelled solid oxide fuel cell cost reduction and synthesize pathways to its commercialisation. The method is applied to 6181 plants in 27 European countries. Results show that 71% cost reduction is required for a medium sized fuel cell to be market driven. Existing incentives can trigger cost reduction by 13–38% but are not able to sustain it until the fuel cell is market driven. Innovations in business models, and incentivising business models instead of technologies can trigger and sustain cost reduction. Results also show that under today’s high capital cost, the number of economically attractive plants required to install fuel cells are lowest when business models are incentivised compared to other interventions. Incentivising new business models to encourage innovation in the sector has more impact that incentivising technologies. The framework is also relevant for creating narratives around the commercialisation of new technologies.
Oluleye O, Teng Y, 2020, A Comparative Assessment of Policies to Support Heat Decarbonisation in an Industrial Site Utility System, 12th International Conference on Applied Energy
Oluleye O, 2020, Reducing Carbon Mitigation costs of Biogas Fuelled Solid Oxide Fuel Cells: An impact of new business models, 15th Conference on Sustainable Development of Energy Water and Environment Systems (SDEWES 2020)
The high cost of the SOFC makes it difficult to achieve win-win between emission reduction and economic benefits. Most studies neglect the CO2abatement costs associated with cleaner technologies, and studies on abatement costs focus on a global perspective, neglecting technology-specific abatement costs. The SOFC abatement cost can be reduced with innovations in business models. In this work a novel enviro-economic framework whose basis is a detailed optimisation of a plant is developed and applied to quantify the impactof new business models (specifically looking at offsetting capital costs by ploughing back operational savings from a high-efficient SOFC) on reducing the CO2abatement cost of biogas fuelled SOFC systems. Case studies show the new business models reduces the abatement cost from 122 to 56 € per ton in Bulgaria, 160 to 92 € per ton in Czech Republic, and 150 to -90 € per ton in the UK.
Oluleye G, 2020, A novel optimisation framework to support increased uptake of low carbon industrial energy systems, Chemical Engineering Transactions, Vol: 81, Pages: 1063-1068, ISSN: 1974-9791
© 2020 Italian Association of Chemical Engineering - AIDIC. All rights reserved. Combustion of fossil fuels in industrial energy systems (IES) is responsible for over 45 % of CO2 emissions. Low Carbon IES will go a long way in achieving the climate goal of the Paris Agreement; yet, uptake of concepts to deliver low carbon IES is slow. Cost and emissions minimisation based optimisation frameworks applied to design and assess IES, though important, are not able to directly quantify the uptake of new technologies to deliver low carbon IES in a country or region. This work presents a novel MINLP framework capable of directly maximing the adoption of low carbon IES within a country and region whilst determining the optimal energy flows and associate costs. The method is applied to a case stufy of 6,181 energy systems in wastewater treatment plants (WWTP) in 27 EU countries to support increased adoption of technology switching (from combustion to electrochemistry), and fuel switching (from natural gas to biogas). Results show that without policy interventions uptake of these measures is only in 0.2 % of the plants located in Denmark, with policy intervention uptake increases to 60 % in more countries. The novel framework shows how the uptake of a new cleaner technology in a country or region can be accelerated.
Oluleye G, Wigh D, Shah N, et al., 2019, A framework for biogas exploitation in Italian waste water treatment plants, Chemical Engineering Transactions, Vol: 76, Pages: 991-996
Copyright © 2019, AIDIC Servizi S.r.l. Effective utilisation of biogas is an important step in increasing usage of renewable energy, due to the great flexibility that solar and wind power in particular lacks. Biogas generated through anaerobic digestion (AD) of sewage sludge addresses environmental concerns together with creating electricity generation potential. There is currently no optimisation-based decision-support framework to determine the best use of biogas from a Waste Water Treatment Plant (WWTP), and provide a market outlook for each of the options. This work proposes a novel multi-period Mixed Integer Linear Program (MILP) model for dispatch and selection of technologies capable of exploiting biogas produced from sludge. The novelty is also highlighted by extrapolating the optimised results to a broader analysis of 855 Italian WWTPs with Population Equivalent (P.E.) > 20,000. The use of real input data provides a unique added value to the work. The modelling framework is applied to several case studies. Results show that 7–23 % savings in operating costs are possible from integrating three systems to exploit biogas, and the trade-offs between capital and operating costs affect the optimal system choice. Furthermore, market driven scenarios are used to analyse how to improve the economic performance.
Oluleye OO, Allison J, Hawker G, et al., 2018, A two-step optimization model for quantifying the flexibility potential of power-to-heat systems in dwellings, Applied Energy, Vol: 228, Pages: 215-228, ISSN: 0306-2619
Coupling the electricity and heat sectors is receiving interest as a potential source of flexibility to help absorb surplus renewable electricity. The flexibility afforded by power-to-heat systems in dwellings has yet to be quantified in terms of time, energy and costs, and especially in cases where homeowners are heterogeneous prosumers. Flexibility quantification whilst accounting for prosumer heterogeneity is non-trivial. Therefore in this work a novel two-step optimization framework is proposed to quantify the potential of prosumers to absorb surplus renewable electricity through the integration of air source heat pumps and thermal energy storage. The first step is formulated as a multi-period mixed integer linear programming problem to determine the optimal energy system, and the quantity of surplus electricity absorbed. The second step is formulated as a linear programming problem to determine the price a prosumer will accept for absorbing surplus electricity, and thus the number of active prosumers in the market.A case study of 445 prosumers is presented to illustrate the approach. Results show that the number of active prosumers is affected by the quantity of absorbed electricity, frequency of requests, the price offered by aggregators and how prosumers determine the acceptable value of flexibility provided. This study is a step towards reducing the need for renewable curtailment and increasing pricing transparency in relation to demand-side response.
Allison J, Bell K, Clarke J, et al., 2018, Assessing domestic heat storage requirements for energy flexibility over varying timescales, Applied Thermal Engineering, Vol: 136, Pages: 602-616, ISSN: 1359-4311
© 2018 The Authors This paper explores the feasibility of storing heat in an encapsulated store to support thermal load shifting over three timescales: diurnal, weekly and seasonal. A building simulation tool was used to calculate the space heating and hot water demands for four common UK housing types and a range of operating conditions. A custom sizing methodology calculated the capacities of storage required to fully meet the heat demands over the three timescales. Corresponding storage volumes were calculated for a range of heat storage materials deemed suitable for storing heat within a dwelling, either in a tank or as an integral part of the building fabric: hot water, concrete, high-temperature magnetite blocks, and a phase change material. The results indicate that with low temperature heat storage, domestic load shifting is feasible over a few days. Beyond this timescale, the very large storage volumes required make integration in dwellings problematic. Supporting load shifting over 1–2 weeks is feasible with high temperature storage. Retention of heat over periods longer than this is challenging, even with significant levels of insulation. Seasonal storage of heat in an encapsulated store appeared impractical in all cases modelled due to the volume of material required.
Oluleye G, Hawkes AD, Allison J, et al., 2018, An optimisation study on integrating and incentivising Thermal Energy Storage (TES) in a dwelling energy system, Energies, Vol: 11, ISSN: 1996-1073
In spite of the benefits from thermal energy storage (TES) integration in dwellings, the penetration rate in Europe is 5%. Effective fiscal policies are necessary to accelerate deployment. However, there is currently no direct support for TES in buildings compared to support for electricity storage. This could be due to lack of evidence to support incentivisation. In this study, a novel systematic framework is developed to provide a case in support of TES incentivisation. The model determines the costs, CO2 emissions, dispatch strategy and sizes of technologies, and TES for a domestic user under policy neutral and policy intensive scenarios. The model is applied to different building types in the UK. The model is applied to a case study for a detached dwelling in the UK (floor area of 122 m2), where heat demand is satisfied by a boiler and electricity imported from the grid. Results show that under a policy neutral scenario, integrating a micro-Combined Heat and Power (CHP) reduces the primary energy demand by 11%, CO2 emissions by 21%, but with a 16 year payback. Additional benefits from TES integration can pay for the investment within the first 9 years, reducing to 3.5–6 years when the CO2 levy is accounted for. Under a policy intensive scenario (for example considering the Feed in Tariff (FIT)), primary energy demand and CO2 emissions reduce by 17 and 33% respectively with a 5 year payback. In this case, the additional benefits for TES integration can pay for the investment in TES within the first 2 years. The framework developed is a useful tool is determining the role TES in decarbonising domestic energy systems.
Oluleye G, Allison J, Kelly N, et al., 2018, A Multi-period Mixed Integer Linear Program for Assessing the Benefits of Power to Heat Storage in a Dwelling Energy System, Editors: Friedl, Klemes, Radl, Varbanov, Wallek, Publisher: ELSEVIER SCIENCE BV, Pages: 1451-1456
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Sechi S, Giarola S, Lanzini A, et al., 2018, An optimization method to estimate the SOFC market in waste water treatment, Editors: Friedl, Klemes, Radl, Varbanov, Wallek, Publisher: ELSEVIER SCIENCE BV, Pages: 415-420
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Sechi S, Giarola S, Lanzini A, et al., 2017, Techno-economic assessment of the effects of biogas rate fluctuations on industrial applications of solid-oxide fuel cells, ESCAPE-27, Publisher: Elsevier, ISSN: 1570-7946
Wastewater treatment is an energy and greenhouse gas intensive process. An important opportunity to reduce both of these quantities is via the use of biogas in co-generation systems. Solid-oxide fuel cells (SOFCs) are the generator types studied in this work.The feasibility of the retrofitting of a wastewater treatment facility fitted with a SOFC combined heat and power energy provision system is assessed including effects of uncertainties in biogas availability on cost and energy performance. A two-stage stochastic optimization framework is proposed to provide feedback on the energy co-generation system design.Results quantify standard deviations in the biogas rate beyond which the SOFC capacity factor might drop below 80 % and change the optimal size of the modules to install.Keywords: solid-oxide fuel cells, stochastic optimization, wastewater treatment, biogas.
Oluleye G, Jiang N, Smith R, et al., 2017, A novel screening framework for waste heat utilization technologies, Energy, Vol: 125, Pages: 367-381, ISSN: 0360-5442
© 2017 Elsevier Ltd Waste heat exploitation improves the energy efficiency of process sites, ensuring lower costs and lower CO2emissions. Technologies such as organic Rankine cycles, absorption chillers, mechanical heat pumps, absorption heat transformers and absorption heat pumps exist to utilize waste heat. Though these technologies make waste heat re-use technically feasible, selection of technologies based on different heat source temperatures still needs to be addressed. In this work, a novel screening approach is proposed to compare technologies considering the waste heat source quality. A methodology is also presented to select technologies for a process site based on the screening results. Since multiple energy form interactions occur, the screening criterion considers the deviation of the actual performance from the ideal performance of technology options, taking into account irreversibilities as a result of finite temperature heat transfer. The tool is applied to screen and select technologies for waste heat sources below 265 °C. Results identify the temperature ranges where technologies have minimum exergy degradation. The framework systematically matches heat source temperatures with technology options compared to a trial and error approach. The framework was applied to an industrial case study to recover 45,660 kW of useful energy from the available waste heat.
Allison J, Bell K, Clarke J, et al., 2017, Domestic thermal storage requirements for heat demand flexibility, Sustainable Thermal Energy Management International Conference
Oluleye G, Smith R, 2016, A mixed integer linear programming model for integrating thermodynamic cycles for waste heat exploitation in process sites, Applied Energy, Vol: 178, Pages: 434-453, ISSN: 0306-2619
© 2016 Elsevier Ltd Thermodynamic cycles such as organic Rankine cycles, absorption chillers, absorption heat pumps, absorption heat transformers, and mechanical heat pumps are able to utilize wasted thermal energy in process sites for the generation of electrical power, chilling and heat at a higher temperature. In this work, a novel systematic framework is presented for optimal integration of these technologies in process sites. The framework is also used to assess the best design approach for integrating waste heat recovery technologies in process sites, i.e. stand-alone integration or a systems-oriented integration. The developed framework allows for: (1) selection of one or more waste heat sources (taking into account the temperatures and thermal energy content), (2) selection of one or more technology options and working fluids, (3) selection of end-uses of recovered energy, (4) exploitation of interactions with the existing site utility system and (5) the potential for heat recovery via heat exchange is also explored. The methodology is applied to an industrial case study. Results indicate a systems-oriented design approach reduces waste heat by 24%; fuel consumption by 54% and CO2 emissions by 53% with a 2 year payback, and stand-alone design approach reduces waste heat by 12%; fuel consumption by 29% and CO2 emissions by 20.5% with a 4 year payback. Therefore, benefits from waste heat utilization increase when interactions between the existing site utility system and the waste heat recovery technologies are explored simultaneously. The case study also shows that the novel methodology can select and design optimal solutions for waste heat exploitation which are technically, economically and environmentally feasible from a range of technology options, heat sources and end-uses of recovered energy.
Oluleye G, Johnson M, Smith R, 2016, Process integration of waste heat upgrading technologies, Process Safety and Environmental Protection, Vol: 103, Pages: 315-333, ISSN: 0957-5820
© 2016 The Institution of Chemical Engineers Technologies such as mechanical heat pumps, absorption heat pumps and absorption heat transformers allow low-temperature waste heat to be upgraded to higher temperatures. This work develops a comprehensive Mixed Integer Linear Program (MILP) to integrate such technologies into existing process sites. The framework considers interactions with the associated cogeneration system (in order to exploit end-uses of upgraded heat within the system and determine their true value), temperature and quantity of waste heat sources and of sinks for the heat upgraded as well as process economics and the potential to reduce carbon dioxide (CO2) emissions. The methodology is applied to an industrially relevant case study. Integration of heat upgrading technologies has potential to reduce total costs by 23%. Sensitivity analysis is also performed to illustrate the effect of changing capital costs and energy prices on the results, and demonstrate the model functionality.
Oluleye G, Smith R, Jobson M, 2016, Modelling and screening heat pump options for the exploitation of low grade waste heat in process sites, Applied Energy, Vol: 169, Pages: 267-286, ISSN: 0306-2619
© 2016 Elsevier Ltd. The need for high efficiency energy systems is of vital importance, due to depleting reserves of fossil fuels and increasing environmental problems. Industrial operations commonly feature the problem of rejecting large quantities of low-grade waste heat to the environment. The aim of this work is to develop methods for the conceptual screening and incorporation of low-temperature heat upgrading technologies in process sites.The screening process involves determination of the best technology to upgrade waste heat in process sites, and the combination of waste heat source and sink temperatures for a technology. Novel simplified models of mechanical heat pumps, absorption heat pumps and absorption heat transformers are proposed to support this analysis. These models predict the ratio of the real performance to the ideal performance in a more accurate way, than previous simplified models, taking into account the effect of changing operating temperatures, working fluids non-ideal behaviour and the system component inefficiencies.A novel systems-oriented criterion is also proposed for conceptual screening and selection of heat pumps in process sites. The criterion (i.e. the primary fuel recovery ratio) measures the savings in primary fuel from heat upgraded, taking into account power required to drive mechanical heat pumps and missed opportunities for steam generation when absorption systems are used.A graphical based methodology is also developed for applying the PRR in process sites and applied to a medium scale petroleum refinery. Results show that applying the PRR yields 9.2% additional savings in primary fuel compared to using the coefficient of performance to screen and incorporate heat pumps.
Oluleye G, Jobson M, Smith R, et al., 2016, Evaluating the potential of process sites for waste heat recovery, Applied Energy, Vol: 161, Pages: 627-646, ISSN: 0306-2619
As a result of depleting reserves of fossil fuels, conventional energy sources are becoming less available. In spite of this, energy is still being wasted, especially in the form of heat. The energy efficiency of process sites (defined as useful energy output per unit of energy input) may be increased through waste heat utilisation, thereby resulting in primary energy savings.In this work, waste heat is defined and a methodology developed to identify the potential for waste heat recovery in process sites; considering the temperature and quantity of waste heat sources from the site processes and the site utility system (including fired heaters and, the cogeneration, cooling and refrigeration systems). The concept of the energy efficiency of a site is introduced – the fraction of the energy inputs that is converted into useful energy (heat or power or cooling) to support the methodology. Furthermore, simplified mathematical models of waste heat recovery technologies using heat as primary energy source, including organic Rankine cycles (using both pure and mixed organics as working fluids), absorption chillers and absorption heat pumps are developed to support the methodology. These models are applied to assess the potential for recovery of useful energy from waste heat.The methodology is illustrated for an existing process site using a case study of a petroleum refinery. The energy efficiency of the site increases by 10% as a result of waste heat recovery. If there is an infinite demand for recovered energy (i.e. all the recoverable waste heat sources are exploited), the site energy efficiency could increase by 33%. The methodology also shows that combining technologies into a system creates greater potential to exploit the available waste heat in process sites.
Oluleye G, Vasquez L, Smith R, et al., 2016, A multi-period Mixed Integer Linear Program for design of residential distributed energy centres with thermal demand data discretisation, Sustainable Production and Consumption, Vol: 5, Pages: 16-28, ISSN: 2352-5509
Distributed Energy (DE) has gained significant interest in recent years as a way to maximise the efficient use of fuel for the production of electricity and heat. The concept of DE is to produce energy close to the end users. The increased fuel efficiency allows a significant reduction in carbon dioxide (CO2) emissions. In this paper, the sizes and the number of heat and power supply units are determined by an optimisation procedure that minimises the total annual cost. A Mixed Integer Linear Programming (MILP) model is developed to design new DE centres from a portfolio of possible technologies to service the thermal and power demand profiles of a geographic region. In this model, the partial load required for the combined heat and power (CHP) units and the equipment operating schedule in time intervals are selected to meet the demand data. The approach requires that energy demand be represented by discrete time bands to model the variations according to the time of day, day of the week and season of the year. Selection of inappropriate time bands can lead to misleading results. In this paper a systematic procedure for selecting time bands is proposed. The optimisation model is demonstrated in a case study. Results indicate that 70%–86% reduction in CO2 emissions is possible relative to individual building heating systems. Including thermal storage in the design of distributed energy centres achieves 54% reduction in CO2 emissions compared to design without thermal storage, since fossil fuelled units are not operated continuously.
Oluleye G, Jobson M, Smith R, 2015, A hierarchical approach for evaluating and selecting waste heat utilization opportunities, Energy, Vol: 90, Pages: 5-23, ISSN: 0360-5442
This paper presents a ranking criterion for evaluating opportunities that utilize recovered energy from the available waste heat in process sites. The ranking criterion takes into account the energy performance of waste heat recovery technologies associated with each opportunity, their potential to reduce greenhouse gas emissions (namely CO2) and the economics (costs and benefits). Mathematical modelling of the opportunities using the ranking criterion is developed to allow for systematic evaluation of opportunities, for example within an optimization framework. A methodology using the ranking criterion to design site waste heat recovery systems is also proposed. The methodology is applied to a case study of a petroleum refinery. Hierarchy and performance of waste heat utilization opportunities depends on the temperature of the heat available, amongst other factors. The site operating cost and CO2 emissions reduce by 26% and 18% respectively when opportunities to use the recovered energy from waste heat within and outside the process site boundaries are explored. Sensitivity of the ranking to energy prices is studied, to explore the outlook for waste heat utilization in the future. The methodology can be applied to the process industries and other facilities producing waste heat.
Oluleye OO, Jobson M, Smith R, 2015, Optimisation-based design of site waste heat recovery systems, ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems
Oluleye OO, Jobson M, Smith R, 2014, Improving a process site sustainability through waste heat recovery, Environmental Division 2014 - Core Programming Area at the 2014 AIChE Annual Meeting 2014, Pages 335-357
Oluleye OO, Jobson M, Smith R, 2014, Optimal design and integration of a process site waste heat recovery system, 2014 AIChE Annual Meeting
Oluleye OO, Jobson M, Smith R, 2014, A hierarchical approach for evaluation of waste heat utilization opportunities, 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, ISSN: 1974-9791
Oluleye OO, Jobson M, Smith R, et al., 2014, Evaluating the potential of a process site for waste heat recovery, 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, ISSN: 1974-9791
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