Selling Surplus Electricity Research Articles

Feasibility of hydrogen hybrid energy systems for sustainable on- and off-grid integration: An Australian REZs case study

The escalating effects of climate change and the finite nature of fossil fuels underscore the imperative for transitioning to renewable energy. This study assesses the feasibility of hybrid energy systems that harness renewable sources, such as solar and wind power, alongside hydrogen technologies and solid-state lithium-ion batteries in diverse energy landscapes. Concentrating on five of Australia's renewable energy zones (REZs)—Broken Hill in New South Wales, Murray River in Victoria, Darling Downs in Queensland, Riverland in South Australia, and North East Tasmania—the research employs the Hybrid Optimization Model for Multiple Energy Resources (HOMER Pro) microgrid software. This software optimizes the sizing of system components to ascertain the most cost-effective configurations for each REZ, considering varied scenarios, including resource availability and demand patterns. The findings indicate that Broken Hill and Murray River exhibit the lowest levelized cost of energy (LCOE) for off-grid and on-grid configurations, respectively, at $0.32/kWh and $0.030/kWh. Conversely, North East Tasmania has the highest LCOE for both configurations, at $0.38/kWh and $0.034/kWh, respectively. Furthermore, the study suggests that beyond grid extension distances of 350–530 km, off-grid solutions may be more economically viable than grid extensions. Moreover, on-grid configurations demonstrate the lowest net present cost (NPC), benefiting from the option to sell surplus electricity back to the utility grid, thereby enhancing their economic advantage over off-grid options. The strategic implications of these results are significant for global energy planning, advocating for a portfolio approach that incorporates a mix of on-grid, off-grid, and extended-grid systems, crucial for sustainably meeting future energy demands. These insights have the potential to guide research, policy, and investment decisions, promoting the cost-efficient deployment of renewable hydrogen hybrid energy systems. The outcomes of this study reinforce that a sustainable energy economy is necessary and achievable through the informed and strategic deployment of technology tailored to geographical and economic specificities.

Techno-economic and environmental assessment of solar photovoltaic, diesel, and electric water pumps for irrigation in Assam, India

This study assesses the techno-economic and environmental aspects of solar photovoltaic (PV), diesel, and electric water pumps for irrigation in Assam, India. Two practical crop rotations are considered: Sali rice, strawberry, and Ahu rice; and Sali rice, mustard, and Boro rice. A comprehensive analysis, including performance, cost-effectiveness, and CO2 emissions, was conducted through field surveys and data analysis. The findings highlight the advantages of solar photovoltaic water pumps (SPVWP), including reduced CO2 emissions, lower operational costs, and the potential revenue from selling surplus electricity generated and participating in carbon trading. The study explores the sensitivity to varying subsidy rates, emphasizing the potential to promote SPVWP adoption through revised policies. Factors like crop rotation, energy costs, and groundwater availability are also considered. SPVWP emerges as a viable and sustainable irrigation solution in Assam and similar regions with appropriate financial incentives and support. The research offers valuable insights for policymakers and advances the understanding of renewable energy-based irrigation systems.

The influence of electricity transaction models on the optimal design of PV and PV-BESS systems

A shift toward more deployment of renewable energy resources has been noticed in the residential sector. Solar photovoltaic (PV) systems, supported by battery energy storage systems (BESS), are considered the most used renewable energy resource at urban scales as they utilize the buildings’ roof and facades to install PV panels. In order to better match the PV electricity solar production pattern with buildings’ demand pattern, multi-objective optimization is used in existing studies. This is extremely important in the residential sector as the time of peak solar production does not coincide with the peak demand occurring in the evening. To this end, this study employs a two-phase optimization framework to explore the influence of the different electricity transaction models on the optimal design of PV and PV-BESS systems when performing the optimization process. A residential neighborhood in downtown Los Angeles, California, is used as a case study to find the optimal system in terms of maximum self-consumption (SC) and self-sufficiency (SS) and minimum payback period (BP) and the load variance over the grid. The results indicate that selling surplus electricity to the grid at Time of Use (TOU) rates used in California influences the optimal configuration of PV and PV-BESS systems. Selling surplus electricity results in more PV panels on the south-west orientations and less on the south-east orientations compared to the scenarios that do not consider trading with the grid. Selling surplus production also impacts the optimal number of batteries needed in PV-BESS systems when the decision maker prefers the payback period objective. In some cases, acheiving higher SS is possible using batteries. However, this may lead to unexpected pressure over the grid. This is due to a huge surplus exported to the grid within a short period of time when batteries are fully charged. The results show that using batteries lowers the load variance over the grid in general and achieves the highest percentage of SS. The scenarios in which there are no batteries added to the system and selling surplus PV production is allowed over the grid achieved the least PB. The scenarios in which the batteries are used and the selling of surplus PV is not allowed, achieved the highest percentage of SC.

Feasibility study of energy storage options for photovoltaic electricity generation in detached houses in Nordic climates

Energy storage is an emerging solution to mitigate the intermittency of solar photovoltaic (PV) power generation and includes several technologies that could also be applied in small-scale residential applications. However, energy storage systems have not yet seen wide-scale integration into the energy systems of buildings, due to the inherently high investment costs of energy storages. Nevertheless, as new EU policies suggest stricter climate targets for 2030, including proposals to increase the share of renewable energy in the building sector to 49 %, a potential widescale integration of solar PV systems combined with various energy storage technologies in many types of buildings could follow. Subsequently, this paper models the use of lithium-ion battery storage (LIB), hydrogen storage, and thermal energy storage (TES) in detached houses in southern Finland, in order to evaluate the cost-effectiveness of utilizing energy storages to enhance residential photovoltaic electricity generation.This study found that solar PV systems without selling surplus electricity to the grid were profitable up to a renewable fraction of 10 % with 2019 market prices and up to 35 % with the 2021 unusually high market prices. The possibility of selling the surplus electricity to the grid improves the profitability further, up to a renewable fraction of 20 % with 2019 market prices and up to 50 % with 2021 market prices. Out of the examined energy storage technologies, LIB storage turned out to be the most financially feasible storage option with costs relatively close to stand-alone solar PV systems in many scenarios, whereas utilizing either hydrogen storage or TES and HP in combination with solar PV systems turned out to be multiple times more expensive than using grid electricity to power detached houses. Consequently, this paper found that integrating energy storage systems with photovoltaic power generation in individual detached houses would require either sustained high electricity market prices or subsidies to be economically viable in the Nordic climate.

Analysis of Latvian Households’ Potential Participation in the Energy Market as Prosumers

The European Union sets targets for the extensive use of renewable energy. Meanwhile, the energy production network is changing and transferring from the classic “producer to consumer” scheme to new operation models, where a small consumer with local renewable energy systems becomes a producer–prosumer, an active energy consumer who is also an energy producer. This study evaluated a potential of Latvian households’ participation in the energy market as prosumers. The analysis was based on an informal prospective extrapolation data evaluation method, based on real historical data from the Central Statistical Bureau of Latvia, annual reports of distribution and transmission system operators, assessments, and the conclusions of relevant experts. In addition, the real performance of a photovoltaic (PV) system was evaluated to get information on the whole year’s energy balance, and to compare it with seasonal electricity price fluctuation. The Latvian electricity transmission system is able to accept about 800 MW of additional new renewable energy source (RES) capacity, so there is a great potential for prosumers. The biggest obstacle for a household’s involvement in the energy market is the lack of support mechanisms and relatively high cost of RES technologies. The results show that with the current dynamics of new microgenerator connections, Latvia will achieve the set goals regarding the involvement of prosumers in the achievement of RES goals only in the next century. In order to attract the public to energy production, the concept of energy community needs to be defined in Latvian legislation, a balanced peer trading mechanism needs to be developed for various RES self-consumption groups willing to sell surplus electricity, and tax policy conditions need to be reviewed for electricity transactions outside the NET (payment system), in order to fully ensure the rights of prosumers.

Improving energy efficiency of commercial buildings by Combined Heat Cooling and Power plants

Commercial buildings play a key-role in the energy consumption of the building sectors. Recent statistics have shown that as the number of commercial buildings is continuously increasing, their effects on energy consumption are expected to grow. These buildings are characterized by high energy demand mainly due to lighting and HVAC requirements. Rooms of energy saving exist by considering that: (i) electricity demands and HVAC requirements occur simultaneously during the day and (ii) both demands are currently satisfied by using separate energy systems. It is apparent that the adoption of polygeneration systems could represent a valid solution to achieve energy savings. To this aim, the paper investigated the profitability of a trigeneration system for commercial buildings, considering a big Do It Yourself shop located in the northern part of Italy, as case study. The analysis was based on (i) energy consumption data collected by energy-audits and (ii) a profit-oriented management strategy for the trigeneration systems proposed in literature. Results showed that trigeneration represents a profitable energy conversion system thanks to revenues achieved by selling surplus electricity and the support of financial mechanism for “High-Efficient” eligibility. In comparison with the currently adopted energy conversion systems, important reductions in energy consumption and CO2 emissions are observed.

Design, exergy and exergoeconomic analysis and optimization of a CCHP + TES for the use in a complex building

The present paper aims at the optimization and exergy and thermoeconomic analyses of a combined cooling, heat, and power generation system equipped with a thermal energy storage for the use in a residential complex with a gas-fueled internal combustion engine as the prime mover. The system is optimized using the direct search method by minimizing annual cost in two cases of using/not using a thermal energy storage. In case of the use of a thermal energy storage, an engine with a capacity of 2 MW and an operating time of 4000 h are found to be optimal, but when a thermal energy storage is included, an engine with a capacity of 2 MW and an operating time of 5268 hours and a thermal energy storage with a capacity of 18.93 m3 are found to be the optimal options. Both systems are evaluated assuming selling/not selling surplus power to the public power grid. The best case for the performance of the system is to use a thermal energy storage and to sell surplus electricity to the grid. In this case versus the case of excluding the thermal energy storage, primary energy consumption, CO2 emission, operating cost of the system, and power purchase from the public grid are decreased by 20.8, 19.5, 14.3 and 17%, respectively while return on capital is increased by 3.1% resulting in 10.7% higher annual cost of the system.

Husk Energy Supply Systems for Sunflower Oil Mills

Together with solar, wind, and hydro renewable energy sources (RES), biomass constitutes an integral part of the high-renewables electricity systems. Considerable feedstocks for electricity generation are process-based residues. Ukraine is the world leader in sunflower seed production, therefore, husk (a by-product of oil production) is a promising biofuel for combustion- based power plants. The plants consume primarily electricity and fossil fuels (natural gas or fuel oil) for steam production. Their usage affects the edible oil production cost and impacts on climate change. The above facts force us to look for alternatives. By-product (husk) utilization can reduce exhaustible energy consumption (fossil fuels and grid electricity) and mitigate climate change. The aim of the study is to make an energy and ecological assessment of biomass energy supply systems. Specifically, the electricity and heat consumption of Ukrainian sunflower oil mills is investigated. Different options of cogeneration systems are analyzed. The preferable mode of combustion-based husk combined heat and power plants is to meet their own heat demand and to sell surplus electricity. Relative gross income and carbon dioxide emission reductions are calculated. Our results show that husk utilization can meet electricity and heat requirements of edible plants. The surplus electricity may be sold to the grid. Husk combined heat and power plants may result in reduction of carbon dioxide by 200–300% and an increase of total income by 24.7–65.7% (compared to conventional energy supply systems).

Estimation of the usage fee for peer-to-peer electricity trading platform: The case of South Korea

The peer-to-peer (P2P) electricity trading platform (ETP) is an electricity-sharing system by which individuals can sell surplus electricity or purchase electricity to meet a deficit in a regional power network. South Korea has allowed energy prosumers to engage in electricity trading from 2016 and is seeking ways to vitalize the electricity trading market. This study aims to estimate the willingness to pay (WTP) of respondents for the monthly usage of P2P ETP by using the contingent valuation method. Of the 1000 Korean respondents, 639 were willing to pay a fee for using the platform. The estimated WTP is KRW 5958.86 (USD 5.50) per month. Moreover, the estimated WTP is higher in respondents who have more background knowledge of the P2P ETP and who pay higher electricity fees. The estimated WTP is lower than the usage fees of existing ETPs in other countries, which is primarily due to Korea's low electricity prices. Furthermore, the estimation results show that enhancing consumer awareness of P2P trading and introducing market strategies based on electricity usage should be considered by electricity trading companies and regulators to enhance P2P ETP usage.

Simulation of combined heat and power in an acidification process using Nanofluids

Improving the energy efficiency of manufacturing facilities, buildings, and homes can be helpful in meeting energy challenges affordably. Combined heat and power (CHP) systems are strong examples of how energy-efficiency technologies can help achieve significant benefits for end-user facilities, utilities, and communities. Use of CHP systems in the industries with significant thermal losses are more suitable. One of those industries are acidifiers. In this study, CHP system is simulated in an acidifier company located in Zanjan. First, the required amount of heat and power for the acidification process is calculated and then by use of thermal dissipations, as the input of the CHP cycle, the CHP system performance and effectiveness is calculated. To improve the efficiencies of heat exchangers in the CHP cycle, Nano-fluids are applied instead of pure working fluids. It will be shown that CuO-water Nano-fluid provides the best thermal efficiency among the considered Nano-fluids. The simulation results demonstrate that the proposed CHP cycle in addition to providing the definitive heat and power required by the acidification process, also produced the extra power of 2.275 MW. This means that; indeed, the acidifier site does not need to receive electricity from the national grid. It has the possibility of selling surplus electricity to the grid. The payback period is estimated about 5.43 years.

Renewables and Storage in Distribution Systems: Centralized vs. Decentralized Integration

The problem of integrating renewables and storage into a distribution network is considered under two integration models: 1) a centralized model involving a retail utility that owns the integration as part of its portfolio of energy resources, and 2) a decentralized model in which each consumer individually owns and operates the integration and is capable of selling surplus electricity back to the retailer in a net-metering setting. The two integration models are analyzed using a Stackelberg game in which the utility is the leader in setting the retail price of electricity, and each consumer schedules its demand by maximizing individual consumer surplus. The solution of the Stackelberg game defines the Pareto front that characterizes fundamental tradeoffs between retail profit of the utility and consumer surplus. It is shown that, for both integration models, the centralized integration uniformly improves retail profit. As the level of integration increases, the proportion of benefits goes to the consumers increases. In contrast, the consumer-based decentralized integration improves consumer surplus at the expense of retail profit of the utility. For a profit regulated utility, the consumer-based integration may lead to smaller consumer surplus than that when no renewable or storage is integrated at either the consumer or the retailer end.

PV 시스템이 적용된 농어촌 주택 표준모델의 에너지 경제성 분석

국가 에너지 소비의 25%를 차지하는 건물에너지의 저감과 귀농인구의 증가에 따른 저에너지 친환경 주택모델의 수요 충족을 위해 EnergyPlus를 사용하여 PV 시스템이 적용된 농어촌 주택 표준모델의 건물에너지요구량을 기반으로 경제성 분석을 하였다. 2가지 타입의 PV 시스템이 적용되었고 발전된 전력을 건물의 냉방기기와 전기기기, 그리고 난방기기에 사용하였다. 계산에 사용된 주택의 연간 건물에너지요구량은 난방이 냉방에 비해 7배 크게 나타났다. Case1과 Case2로 나누어 PV 시스템의 경제성분석을 실시한 결과, Case1은 냉난방 및 전기기기에 발전된 전력을 사용하고 판매하는 것이, Case2는 냉방과 전기기기에만 전력을 사용하고 전량 판매하는 것이 경제적으로 유리한 것으로 판단된다. 하지만, 향후 전력 판매가격과 가스가격이 변동되면 결과는 달라질 수 있다. 초기투자비용은 Case1이 약 13년, Case2는 약 11년이 지나면 회수되는 것으로 나타났다. Case2가 초기설치비용이 비싸지만 회수기간이 지나면 Case1보다 약 3배 더 많은 이익을 얻을 수 있어 수명연한인 25년 이상 사용 시 경제성 측면에서 유리할 것으로 판단된다. The energy economic analysis of the standard rural house model with PV system was performed based on annual energy demand calculation using the EnergyPlus to contribute in reducing building energy which occupies 25% of national energy consumption and in developing a low-energy & eco-friendly house model. Two types of PV system installation was considered to cover electricity demand for cooling, electric, and heating devices. For the selected house model, heating energy demand is 7 times higher than cooling energy demand. For the Case1, it is favorable to use electricity from PV system for cooling and electric devices and to sell surplus electricity. For the Case2, it is favorable to use electricity from PV system for cooling, electricity and heating devices and to sell surplus electricity. Considering the installation cost of PV system and heat pump air conditioning system, the break-even point of Case1 and Case2 are about 13 and 11 years respectively. Although the installation cost of Case2 is more expensive, Case2 provides three times more profit than Case1 after the break-even point. Because the expected average life time of the selected PV system is 25 years, Case2 is more favorable option for the given standard rural house model.

Feasibility analysis of medium-sized hotel's electrical energy consumption with hybrid systems

Abstract In this study, the case of meeting a hotel's electrical energy demand with hybrid systems has been examined by using four different scenarios. The HOMER program is used for different analyses. In the first case, when the renewable energy resources are insufficient, electrical energy is purchased from grid and in the cases, in which the production is much more than the need, electricity is sold to the grid. In three other cases, the electric demand of the hotel is met by using renewable energy and the amount, which is more than the need, is sold to the grid. As a result, at the present circumstances two scenarios were determined feasible. When the grid is used only selling surplus electricity and the electricity need of the hotel are met by only renewables, battery groups and converters are needed. So, this causes an increase in investment costs. Therefore, these situations must be supported with adequate incentives, to make these systems become more eligible.

Impact of demand load size on strategies for reliable process heat supply

When providing high-temperature process steam to a user such as a chemical plant, high availability and reliability are necessary to maintain production and avoid sudden, unscheduled shutdowns with potentially adverse investment consequences. Therefore, the availability and reliability requirements are expected to be higher than those applicable to dedicated electric power plants. This paper evaluates the impact of the size of the process steam demand on the effectiveness of different approaches for meeting these high reliability requirements using High Temperature Reactor (HTR) process steam supply systems. Such systems will require significant backup redundancy, since individual reactor modules have inherently lower availability than that required by a process heat plant. Systems using additional HTRs and systems using traditional gas-fired boilers for backup capacity are both analyzed. Potential system configurations are analyzed for a wide range of process heat plant steam demands, from 200MWt to 1500MWt. The analysis includes availability analysis, assessment of overall redundancy, and economic evaluation. Consideration is also given to the benefit of selling surplus electricity generated with excess steam. Finally, the sensitivity of different plant configurations to fossil fuel price volatility is discussed briefly.

Improving bioethanol production from sugarcane: evaluation of distillation, thermal integration and cogeneration systems

Demand for bioethanol has grown considerably over the last years. Even though Brazil has been producing ethanol from sugarcane on a large scale for decades, this industry is characterized by low energy efficiency, using a large fraction of the bagasse produced as fuel in the cogeneration system to supply the process energy requirements. The possibility of selling surplus electricity to the grid or using surplus bagasse as raw material of other processes has motivated investments on more efficient cogeneration systems and process thermal integration. In this work simulations of an autonomous distillery were carried out, along with utilities demand optimization using Pinch Analysis concepts. Different cogeneration systems were analyzed: a traditional Rankine Cycle, with steam of high temperature and pressure (80 bar, 510 °C) and back pressure and condensing steam turbines configuration, and a BIGCC (Biomass Integrated Gasification Combined Cycle), comprised by a gas turbine set operating with biomass gas produced in a gasifier that uses sugarcane bagasse as raw material. Thermoeconomic analyses determining exergy-based costs of electricity and ethanol for both cases were carried out. The main objective is to show the impact that these process improvements can produce in industrial systems, compared to the current situation.

Optimal synthesis of trigeneration systems subject to environmental constraints

Environmental information obtained through Life Cycle Analysis techniques has been incorporated into a Mixed Integer Linear Programming (MILP). The solution of the model provides the optimal configuration and operation of an energy supply system to be installed, minimizing the environmental burden associated with production of equipment and consumption of resources. Starting from a superstructure of cogeneration system with additional components highly interconnected, the energy supply system was optimized considering specific demands of a hospital located in Zaragoza, Spain. The objective functions took into account the kilograms of CO 2 released and Eco-indicator 99 Single Score. Also considered were price of energy resources, price and amortization possibilities of the equipment and options for selling surplus electricity to the electric grid. The effect of electricity generation conditions on the optimal configuration was examined by varying the source of electricity production in Spain and considering natural gas/electricity mixes from alternate countries. The ratio between local electricity emissions and natural gas emissions ( α factor) was found to have the highest impact on the configuration of the system. Therefore the α factor could be considered the strongest influencing factor when deciding the optimal configuration of a system that minimizes environmental loads.

Feasibility of husk-fuelled steam engines as prime mover of grid-connected generators under the Thai very small renewable energy power producer (VSPP) program

Rice husk generated as a by-product of rice mill processes can be utilized as an energy source for husk-fuelled rice mills. The economic evaluation of the investment of husk-fuelled steam engine rice mills, which generate mechanical energy for the direct driving of milling equipments, has previously been presented in literature. It was reported that for some particular conditions of rice mill, the investment of husk-fuelled steam engine as energy-saving technology is financially feasible. Since May 2002, electricity distributors in Thailand have allowed renewable energy producers up to 1 MW to connect their generators to the grid in order to sell surplus electricity to the grid. This arrangement creates more income opportunities for husk-fuelled steam engine owners to generate not only mechanical power for rice milling processes, but also surplus electricity for feeding onto the grid. The objective of this study is to investigate the financial feasibility of the investment in a husk-fuelled steam engine system which drives grid-connected electrical generators, reduces rice mill demand and electricity and sells surplus electricity to the grid. The technical and economic data for rice mill sizes 35, 45, 60, 95 and 120 t/d presented in this study show that the husk-fuelled steam engine system with grid-connected generators improves the economic performance of applying the system solely for the largest 120 t/d rice mills. However, the conventional husk-fuelled steam engine without electric generator gives a better economic performance of the rice mills sizes from 45 to 95 t/d.

98/03240 Reciprocating steam engine power plants fed by woodwaste

Rice husk generated as a by-product of rice mill processes can be utilized as an energy source for husk-fuelled rice mills. The economic evaluation of the investment of husk-fuelled steam engine rice mills, which generate mechanical energy for the direct driving of milling equipments, has previously been presented in literature. It was reported that for some particular conditions of rice mill, the investment of husk-fuelled steam engine as energy-saving technology is financially feasible. Since May 2002, electricity distributors in Thailand have allowed renewable energy producers up to 1 MW to connect their generators to the grid in order to sell surplus electricity to the grid. This arrangement creates more income opportunities for husk-fuelled steam engine owners to generate not only mechanical power for rice milling processes, but also surplus electricity for feeding onto the grid. The objective of this study is to investigate the financial feasibility of the investment in a husk-fuelled steam engine system which drives grid-connected electrical generators, reduces rice mill demand and electricity and sells surplus electricity to the grid. The technical and economic data for rice mill sizes 35, 45, 60, 95 and 120 t/d presented in this study show that the husk-fuelled steam engine system with grid-connected generators improves the economic performance of applying the system solely for the largest 120 t/d rice mills. However, the conventional husk-fuelled steam engine without electric generator gives a better economic performance of the rice mills sizes from 45 to 95 t/d.