Polygeneration Applications Research Articles

Multi-criteria optimization next to a comparative analysis of a polygeneration layout based on a double-stage gas turbine cycle fueled by biomass and hydrogen

The significance and advantages of utilizing renewable energy sources are widely recognized. Upon examining past studies, it was revealed that there has been a lack of research on harnessing the waste energy from double-stage gas turbines powered by biomass-hydrogen hybrid fuel for polygeneration applications. Thus, a new configuration is proposed in the study for the multi-production of electricity, cooling, heating, and potable water. In the current research, a high-pressure turbine is driven by a combustion chamber fed by a biomass gasifier. Meanwhile, a low-pressure turbine is driven by a post-combustion chamber fed by hydrogen as fuel. The heat loss of the topping gas turbine cycle is recuperated by a supercritical Brayton cycle (SBC), a steam Rankine cycle (SRC), and a water heater. The waste heat of the supercritical Brayton cycle and steam Rankine cycle is recovered through an absorption refrigeration cycle and a thermoelectric generator, respectively. Thus, the heat loss of the topping system is completely recovered. The net power output of the gas turbine cycle is considered the electricity production of the system while the output power of the SBC and SRC is utilized in a reverse osmosis desalination system to produce potable water. The investigations conducted on the system are thermodynamic and exergy-economic assessments and three-objective optimization utilizing 5 gases (i.e., CO2, CO, Nitrogen, Air, and Helium) in the SBC. The final results reveal the superiority of Helium as the supercritical gas, bringing about an exergy efficiency () of 32.11%, a total cost rate () of 103 , a payback period (PP) of 0.159 years, and a specific cost of polygeneration () of 22.03 for the system. Although the levelized cost of products of the configuration is high due to the freshwater production, of the proposed system is higher than the previous systems based on a double-stage gas turbine cycle driven by biomass and hydrogen.

Performance map analysis of a solar-driven and fully unfired closed-cycle micro gas turbine

This work deals with the performance maps analysis of an unfired micro gas turbine (MGT) integrated in a Concentrating Solar Power plant aimed at polygeneration applications. Particularly, this contribution explores the applicability of a MGT in a closed and unfired power cycle driven by a mass flow rate regulation system. The new layout and the system components pressure drops determine the variation of the nominal MGT working points; for that both the influence of the new operating conditions and that of the pressure drops on engine performance were analyzed. Three operational strategies were considered in which the pressure drops have been set. Furthermore, the recuperator design has been carried out and its off-design map has been obtained. The commercial MGT data were assumed, supposing it operates in a pressurized cycle with a limited turbine inlet temperature. The results show that by increasing the inlet pressure within the machinery it is possible to achieve, in highly constrained conditions, a power of almost 500 kWe with an efficiency of 32%, while in more performing ones the peak power is approx. 570 kWe and the efficiency is around 34%. Finally, the recuperator design results showed an effectiveness of 91.75% at these operating conditions.

Recent advances, challenges, and prospects in solar dish collectors: Designs, applications, and optimization frameworks

The use of solar powered dish-Stirling engines to convert thermal energy into electricity is a promising and renewable alternative in reducing the fossil fuel consumption. However, insufficient experimental data regarding the operating parameters limit its characterization, modelling, design, optimization, and further utilization. Therefore, the first aim of this paper is to introduce a comprehensive review and systematic summary of state of the art on research and progress of the solar dish technology as a concentrated solar power technology. The efforts mainly include the recent advances, technological challenges, and optimization frameworks in solar dish collector research field. One of the most critical features of this study is discussing novel combinations of solar dish collectors with other power generation devices including PV cells, thermoelectric devices, and thermal collectors. The review sheds light also into recent thermodynamic cycles that can be powered by solar dish collector as well potential polygeneration applications that can be engineered. Further, the most relevant researches adopting Nanofluids and Phase Change Materials in solar dish collectors are reviewed. In the final part, future prospects and challenges that require further investigation are also discussed. It is expected that this review will serve as a brief guideline for the solar dish-technology enthusiast.

Solar Dish Stirling technology for sustainable power generation in Southern Morocco: 4-E analysis

This paper presents an energy, exergy, economic and environmental assessment of the Solar Dish Stirling (SDS) technology in thirteen Southern Moroccan sites, carrying out parametric analysis of various design parameters to optimise this technology under time-varying climatic data. System simulation was conducted on an hourly basis with the help of System Advisor Model (SAM) software. Annual energy can be maximised by adjusting the receiver aperture diameter, cooling pump speed, and thickness of receiver insulation appropriately. For all examined sites, the optimum value of the receiver aperture diameter and the thickness of receiver insulation were 70 mm and 30 mm, respectively. The recommended value of the pump speed varies depending on meteorological parameters for each site. The highest annual energy yield considering the optimal values of the assessed parameters is achieved in the site of Ouarzazate, which for a total installed capacity of 10 MW, reached a value of 23.693 GWh. Annual overall energetic and exergetic efficiencies were determined to be 24.26% and 25.98%, respectively. Nominal Levelized Cost of Electricity in the various cities varied in the range of 10.87c$/kWh and 18.69c$/kWh for Ouarzazate and Tan-Tan, respectively. Environmentally, the SDS technology can mitigate between 7.76 ktonne and 13.85 ktonne of CO2 emissions annually. Top three potential sites for implementing the Solar Dish Stirling technology were identified as Ouarzazate, Errachidia, and Midelt, assisting Moroccan policymakers in developing strategies to promote and plan future projects. Solar Dish Stirling technology can open the perspectives for modern polygeneration applications that can promote living conditions in Morocco’s southern regions.

Solar organic Rankine cycle and its poly-generation applications – A review

The solar Organic Rankine Cycle system seems to be one of the most reliable renewable energy-based technologies to satisfy major energy demands. Solar organic Rankine cycle based poly-generation systems are energy-efficient systems that can generate various useful energy outputs, including electricity, heating, cooling, drying, desalination, and hydrogen. As a result, combining solar organic Rankine systems with poly-generation units is the most efficient way of generating multiple useful outputs while still using a renewable energy source. The present review study focuses on exploiting the solar organic Rankine cycle and its poly-generation applications. Novel experimental and numerical study of different researchers focusing on the Solar Organic Rankine cycle with different solar collectors’ integration along with different organic working fluids are discussed in this paper. The review study mainly focuses on the cogeneration, trigeneration, and poly-generation applications of the solar organic Rankine cycle. In the end, the future scope part of this study will surely help the researcher and engineers for further improvement in the solar organic Rankine system.

A comprehensive review analysis on advances of evacuated tube solar collector using nanofluids and PCM

Solar thermal energy is extensively used in industrial and domestic applications like solar drying operation, space heating, water heating, desalting of water, etc. A solar collector is used to convert solar irradiance into thermal energy. By far, Evacuated tube solar collector is the most extensively used solar thermal collector in the market due to less convective losses. Different types such as (heat pipe, thermosiphon, U-Tube) were used by different researchers. Different geometrical modification techniques like integrating reflectors and fins integrated heat pipes were used by various researchers for thermal performance enhancement, but the revolutionary enhancement in its thermal performance was observed when nanofluids and Phase Change Materials were used with the Evacuated tube solar collector. Different numerical models to calculate its energy and exergy performance as well as economic and environmental impacts of the Evacuated tube solar collector are summarized in this review. Cogeneration, trigeneration, and poly-generation applications of the evacuated tube solar collector part will motivate the researchers to generate multiple energy from a single input source simultaneously. Future scope and recommendation part of this paper will help the researchers and practice engineers who want to work on the Evacuated tube solar collector to improve its thermal performance.

Performance assessment of a 15 kW Micro-CHCP plant through the 0D/1D thermo-fluid dynamic characterization of a double water circuit waste heat recovery system

The exploitation of renewable energy sources and the use of primary energy saving techniques have been recognized as key solutions to face climate changes. The consequent energy policies are pushing the transition from a centralized power generation system to a distributed polygeneration system able to meet simultaneous heating, cooling and electricity demand. However, small scale polygeneration plants do not ensure any primary energy and cost saving without a proper sizing and operation of the plant. Furthermore, a flexible configuration of the waste heat recovery system (WHRS) adopted for polygeneration purposes can be equally important. Therefore, starting from the experimental data concerning a 15 kW micro-CHP plant previously designed and prototyped, the paper addresses the performance assessment of a CHCP plant configuration based on the same basic engine-electric generator system through the 1D thermo-fluid dynamic characterization of an alternative double water circuit WHRS. This configuration, delivering thermal power at different temperature level, could be useful to meet thermal and cooling demand from different user or when seasonal energy demand occurs. This paper also provides an effective approach for the design of WHRS which are capable to ensure a reasonable matching between the temperature level required by the user and that provided by the plant. In this way, being the energy saving dependent on the thermal power recovered and actually exploited, and so on the temperature level which characterizes the user's heat demand, primary energy savings are more easily achievable even when small scale polygeneration applications are considered. Results shows the possibility of supplying an absorption chiller and obtaining a coolling capacity of about 10.5 kW from the resulting CHCP plant configuration.

Cold recovery from LNG-regasification for polygeneration applications

Liquefied Natural Gas (LNG) has a high exergetic potential because of its low temperature (around −162 °C), although usually the cold released from LNG regasification is wasted. In this paper, the LNG supply chain and the conventional regasification technologies are reviewed and analyzed to identify the cold recovery opportunities. Also, an overview of the applications and technologies for LNG cold recovery is presented. Although there many applications and technologies for this purpose, most of them are immatures and their implementation is not widespread. Besides, most of the literature is focused on exploiting LNG cold for a single application, while LNG cold offers a lot of possibilities of exploitation via polygeneration. In the second part of this paper, a polygeneration plant for power and cold production is proposed and modelled as a case study for cold recovery from LNG-regasification. The structure of the plant is engineered to operate with high flexibility. The LNG exergy is exploited in cascade for power production and cold generation in a district cooling network with three different temperature levels. The plant achieves an equivalent energy saving of 81.1 kW h/ton-LNG with an exergetic efficiency of 34.7%. The seawater consumption is reduced 67.6% respect to the typical LNG regasification.

Operational Optimization of a Typical micro Gas Turbine

Micro Gas Turbines (mGTs) offer great potential for use in co-, tri or polygeneration applications. In these applications, where the heat from the exhaust gases is used in an efficient way, the mGTs achieve very high efficiencies. To be able to determine the number of units, the nominal parameters of the units and the specific operating strategy of the mGT, it is key to know precisely the performance of these units. Generally in co-, tri- or polygeneration applications with mGTs, this performance is considered to be known and fixed, and is therefore directly used to determine the operational strategy of the network, possibly linked with an economic analysis. In real world operating conditions, the parameters characterizing the operation of the mGT are measured with uncertainties. Depending on the model sensitivity to input parameters, these uncertainties may have a tremendous effect on the performance of the mGT. These uncertainties should be taken into consideration by the designers in an early stage of the design process to achieve a so-called robust design. In this paper, we present the operational optimization of a typical mGT, the Turbec T100 mGT, using a deterministic approach. In this approach, the parameter uncertainties are not taken into account, however, it is an important first step towards a full robust design, since it will set the reference. By varying Turbine Outlet Temperature (TOT) and compressor rotational speed, a Pareto front for maximal electrical power output and electrical efficiency is found. The two objectives are conflicting, making that the maximal electrical efficiency cannot be reached at maximal electrical power output. The results of this optimization will be used in our future study on the design optimization under uncertainties.

Experimental and numerical investigation of pellet and black liquor gasification for polygeneration plant

It is vital to perform system analysis on integrated biomass gasification in chemical recovery systems in pulp and paper and heat and power plants for polygeneration applications. The proposed integration complements existing pulp and paper and heat and power production systems with production of chemicals such as methane and hydrogen. The potential to introduce gasification-based combined cycles comprising gas turbines and steam turbines to utilize black liquors and wood pellets also merits investigation. To perform such analysis, it is important to first build knowledge on expected synthesis gas composition by gasifying at smaller scale different types of feed stock. In the present paper, the synthesis gas quality from wood pellets gasification has been compared with black liquor gasification by means of numerical simulation as well as through pilot-scale experimental investigations. The experimental results have been correlated into partial least squares models to predict the composition of the synthesis gas produced under different operating conditions. The gas quality prediction models are combined with physical models using a generic open-source modelling language for investigating the dynamic performance of large-scale integrated polygeneration plants. The analysis is further complemented by considering potential gas separation using modern membrane technology for upgrading the synthesis gas with respect to hydrogen content. The experimental data and statistical models presented in this study form an important literature source for future use by the gasification and polygeneration research community on further integrated system analysis.

Review of optimization techniques of polygeneration systems for building applications

Polygeneration means simultaneous production of two or more energy products in a single integrated process. Polygeneration is an energy-efficient technology and plays an important role in transition into future low-carbon energy systems. It can find wide applications in utilities, different types of industrial sectors and building sectors. This paper mainly focus on polygeneration applications in building sectors. The scales of polygeneration systems in building sectors range from the micro-level for a single home building to the large- level for residential districts. Also the development of polygeneration microgrid is related to building applications. The paper aims at giving a comprehensive review for optimization techniques for designing, synthesizing and operating different types of polygeneration systems for building applications.

Fuel Composition Transients in Fuel Cell Turbine Hybrid for Polygeneration Applications

Transient impacts on the performance of solid oxide fuel cell/gas turbine (SOFC/GT) hybrid systems were investigated using hardware-in-the-loop simulations (HiLSs) at a test facility located at the U.S. Department of Energy, National Energy Technology Laboratory. The work focused on applications relevant to polygeneration systems, which require significant fuel flexibility. Specifically, the dynamic response of implementing a sudden change in fuel composition from syngas to methane was examined. The maximum range of possible fuel composition allowable within the constraints of carbon deposition in the SOFC and stalling/surging of the turbine compressor system was determined. It was demonstrated that the transient response was significantly impact the fuel cell dynamic performance, which mainly drives the entire transient in SOFC/GT hybrid systems. This resulted in severe limitations on the allowable methane concentrations that could be used in the final fuel composition when switching from syngas to methane. Several system performance parameters were analyzed to characterize the transient impact over the course of 2 h from the composition change.

Effect of the type of gasifying agent on gas composition in a bubbling fluidized bed reactor

It is commonly accepted that gasification of coal has a high potential for a more sustainable and clean way of coal utilization. In recent years, research and development in coal gasification areas are mainly focused on the synthetic raw gas production, raw gas cleaning and, utilization of synthesis gas for different areas such as electricity, liquid fuels and chemicals productions within the concept of poly-generation applications. The most important parameter in the design phase of the gasification process is the quality of the synthetic raw gas that depends on various parameters such as gasifier reactor itself, type of gasification agent and operational conditions. In this work, coal gasification has been investigated in a laboratory scale atmospheric pressure bubbling fluidized bed reactor, with a focus on the influence of the gasification agents on the gas composition in the synthesis raw gas. Several tests were performed at continuous coal feeding of several kg/h. Gas quality (contents in H2, CO, CO2, CH4, O2) was analyzed by using online gas analyzer through experiments. Coal was crushed to a size below 1 mm. It was found that the gas produced through experiments had a maximum energy content of 5.28 MJ/Nm3 at a bed temperature of approximately 800 °C, with the equivalence ratio at 0.23 based on air as a gasification agent for the coal feedstock. Furthermore, with the addition of steam, the yield of hydrogen increases in the synthesis gas with respect to the water–gas shift reaction. It was also found that the gas produced through experiments had a maximum energy content of 9.21 MJ/Nm3 at a bed temperature range of approximately 800–950 °C, with the equivalence ratio at 0.21 based on steam and oxygen mixtures as gasification agents for the coal feedstock. The influence of gasification agents, operational conditions of gasifier, etc. on the quality of synthetic raw gas, gas production efficiency of gasifier and coal conversion ratio are discussed in details.

Steam gasification of various feedstocks at a dual fluidised bed gasifier: Impacts of operation conditions and bed materials

Gasification of biomass is an attractive technology for combined heat and power production as well as for synthesis processes such as production of liquid and gaseous biofuels. Dual fluidised bed (DFB) technology offers the advantage of a nearly nitrogen-free product gas mainly consisting of H2, CO, CO2 and CH4. The DFB steam gasification process has been developed at Vienna University of Technology over the last 15 years using cold flow models, laboratory units, mathematical modelling and simulation. The main findings of the experimental work at a 100-kW pilot scale unit are presented. Different fuels (wood pellets, wood chips, lignite, coal, etc.) and different bed materials (natural minerals such as olivine, limestones, calcites, etc. as well as modified olivines) have been tested and the influence on tar content as well as gas composition was measured and compared among the different components. Moreover, the influence of operating parameters such as fuel moisture content, steam/fuel ratio and gasification temperature on the product gas has been investigated. DFB steam gasification of solid biomass coupled with CO2 capture, the so-called absorption enhanced reforming (AER) process, is highlighted. The experiments in pilot scale led to commercial realisation of this technology in demonstration scale. Summarising, the DFB system offers excellent fuel flexibility to be used in advanced power cycles as well as in polygeneration applications.

Biomass gasification in district heating systems – The effect of economic energy policies

Biomass gasification is considered a key technology in reaching targets for renewable energy and CO 2 emissions reduction. This study evaluates policy instruments affecting the profitability of biomass gasification applications integrated in a Swedish district heating (DH) system for the medium-term future (around year 2025). Two polygeneration applications based on gasification technology are considered in this paper: (1) a biorefinery plant co-producing synthetic natural gas (SNG) and district heat; (2) a combined heat and power (CHP) plant using integrated gasification combined cycle technology. Using an optimisation model we identify the levels of policy support, here assumed to be in the form of tradable certificates, required to make biofuel production competitive to biomass based electricity generation under various energy market conditions. Similarly, the tradable green electricity certificate levels necessary to make gasification based electricity generation competitive to conventional steam cycle technology, are identified. The results show that in order for investment in the SNG biorefinery to be competitive to investment in electricity production in the DH system, biofuel certificates in the range of 24–42 EUR/MWh are needed. Electricity certificates are not a prerequisite for investment in gasification based CHP to be competitive to investment in conventional steam cycle CHP, given sufficiently high electricity prices. While the required biofuel policy support is relatively insensitive to variations in capital cost, the required electricity certificates show high sensitivity to variations in investment costs. It is concluded that the large capital commitment and strong dependency on policy instruments makes it necessary that DH suppliers believe in the long-sightedness of future support policies, in order for investments in large-scale biomass gasification in DH systems to be realised.

Harmonic Distortion Analysis of a Micro Gas Turbine Interconnected to the Electricity Grid

Micro gas turbines have opened new opportunities for integrated energy systems using thermally activated technologies for waste heat recovery, improved overall efficiency and reduced emissions in commercial buildings and other small-scale polygeneration applications. However some issues are still unclear, such as the legal and technical issues regarding the electric grid interconnection. In this paper both issues will be addressed from the point of view of the electric system protections and the power quality supply with respect to harmonic distortion. The objective is to provide data and analyse the harmonic distortion of a low-pressure natural gas micro gas turbine of 28 kWe interconnected to the grid. Additionally the main interconnection requirements and protection systems will be described. The studied micro gas turbine cogeneration system is located in the Technological Innovation Centre CREVER at the University Rovira i Virgili in Tarragona (Spain). The results obtained show that the harmonic distortion is clearly below the limits recommended by the existing international standards. Also the already built-in microturbine interconnection protections are enough to assure the correct operation and safety of the micro turbine system and the external grid. However increased communications and automation will be required to manage large amounts of distributed micro gas turbines generation systems connected to the grid.