• Energy Research

Combined Heat and Power (CHP) systems are considered as a transitional solution towards zero carbon emissions in the next couple of decades. The current CHP systems are mainly controlled by thermal led strategy, that is, the electrical power generation depends on the thermal energy demand. The mismatch between the power generation and load demand leads to the deficient energy utilisation and economic loss. An innovative combined planning method is proposed in the paper to improve the economic gains of the CHP systems by integrating the lithium-ion battery storage system (LBSS). The paper focuses on the simultaneous optimisation of storage capacity design and operation strategy formulation of the LBSS subject to the variations of the load and power generation from CHP with consideration of LBSS degradation and cost, and Time-of-Use pricing structures. The new strategy is implemented and tested using the University of Warwick campus CHP system combined with the LBSS facilities. The results show that the method could improve the economic performance of CHP systems. The developed method is applicable to any CHP systems optimisation with integrated LBSS.

Abstract To effectively utilize waste heat resulted in industrial production processes, this study investigates the dynamic thermal management using phase change material (PCM) thermal storage technique for the heat recovery system. The heat transfer process of a tube-type PCM storage module is analyzed and the dynamic model is developed for the optimization of system operation. The flag to indicate different working modes of the storage module is introduced as a system decision variable, which is used in developing an intelligent algorithm adopting biogeography-based optimization method for dynamic control of the system. The effectiveness of the dynamic model is verified via real demonstration experimental tests and the maximum relative error is 5.47%. The validation of the algorithm and evaluation of the dynamic thermal management are carried out by applications in the heat recovery of the steel sintering process. The influences of phase change enthalpy on the system performance are further studied to highlight the role of latent heat in thermal management. Results show that the proportions of fuel consumed in the off, flat and high peak energy utilization sections are optimized from the original 1:6.95:21.71 to 1:2.57:7.02 through the peak shaving and the total consumption of fuel per day is decreased from 6.81 t to 6.34 t. When the phase change enthalpy is reduced from 103 kJ kg−1 to 1 kJ kg−1, the decrease of the energy recovered by the PCM modules leads to the additional 0.06 t fuel consumption per day.

Thermal energy storage using the latent heat of phase change materials (PCMs) is a promising technique to solve the time mismatch between the availability and usage of flue gas heat in distributed generation systems (DGSs). A diesel-engine-powered DGS integrated with two-stage tube-type PCM modules for exhaust gas heat recovery was developed and studied. Energy and exergy analysis for the PCM storage unit was carried out to verify the effectiveness of the PCM modules for heat recovery and to highlight the merits of the cascaded configuration through a practical engineering case. Furthermore, the performance of the DGS was evaluated to study the contribution of PCM storage to improving system efficiency. The results showed that 56.4% energy and 48.3% exergy of the input flue gas were stored by the two-stage storage unit. Additional integration of the low-temperature PCM module to the high-temperature module improved the average storage efficiency from 33.6% to 62.3% for energy and 33.1% to 50.8% for exergy. By utilizing the stored energy for heating water, the thermal efficiency of the diesel engine was increased from the original 35.8% to 41.9%, while the exergy efficiency was improved from 29.5% to 29.7%.

A dynamic modeling framework based on an intelligent approach is proposed to identify the complex behaviors of solid-gas sorption systems. An experimental system was built and tested to assist in developing a model of the system performance during the adsorption and desorption processes. The variations in the thermal effects and gaseous environment accompanying the reactions were considered when designing the model. An optimization platform based on a multi-population genetic algorithm and artificial criteria was established to identify the modeling coefficients and quantify the effects of condition changes on the reactions. The calibration of the simulation results against the tested data showed good accuracy, where the coefficient of determination was greater than 0.988. The outcome of this study could provide a modeling basis for the optimization of solid-gas sorption systems and contribute a potential tool for uncovering key characteristics associated with materials and components.

Although the penetration of renewable energy in power systems has been substantially increased globally in the last decade, fossil fuels are still important in providing the essential flexibility required to reliably maintain the system balance. In 2019, more than one quarter of power generation in Europe and over 40% of the UK’s electricity generation was from fossil fuels (mainly gas). For achieving the net-zero greenhouse gas emission target around the middle of this century, these fossil fuels have to be decarbonised in the coming decades. Bulk-scale energy storage has been recognised as a key technology to overcome the reduced dispatchability associated with the decrease of fossil fuels in generation. Taking the UK power system as a case study, this paper presents an assessment of geological resources for bulk-scale compressed air energy storage (CAES), and an optimal planning framework for CAES in combination with solar and wind to replace fossil fuels in the power generation system. The analysis reveals up to 725 GWh of ready-to-use capacity by utilising existing underground salt caverns in the UK. These potential CAES sites with added solar and wind generation equal to the generation from fossil fuels in 2018 can reduce carbon emissions by 84% with a cost increase by 29%, compared to the system in 2018. The results indicate the plausibly achievable cost-effectiveness of CAES as bulk-scale energy storage for power system decarbonisation in countries the geological resources are available.\ud \ud

A capacity-regulation system based on a novel rotary control valve for reciprocating refrigeration compressor is proposed and designed for the first time. The regulation system is mainly composed of a rotary control valve and an adaptive regulation system. The structure and working principle of the rotary control valve is described in detail, and the control process of the adaptive regulation system for the valve is studied together with the program design. In addition, the parameters for the design and control of the rotary control valve are theoretically determined. To verify the feasibility and effectiveness of the proposed system, a three-cylinder reciprocating compressor was adopted as a test device. Experimental results showed that the technology was able to realize continuous stepless capacity regulation for the compressor within the range of (0)10-100%, and power consumption decreased correspondingly with the load reduction. (C) 2013 Elsevier Ltd and IIR. All rights reserved.

Current power systems are still highly reliant on dispatchable fossil fuels to meet variable electrical demand. As fossil fuel generation is progressively replaced with intermittent and less predictable renewable energy generation to decarbonize the power system, Electrical energy storage (EES) technologies are increasingly required to address the supply-demand balance challenge over a wide range of timescales. However, the current use of EES technologies in power systems is significantly below the estimated capacity required for power decarbonization. This paper presents a comprehensive review of EES technologies and investigates how to accelerate the uptake of EES in power systems by reviewing and discussing techno-economic requirements for EES. Individual EES technologies and power system applications are described, which provides guidance for the appraisal of specific EES technologies for specific power system services. Plausibly required scales and technology types of EES over different regions are then reviewed, followed by discussions on storage cost modelling and predictions for different EES technologies. Opportunities and challenges in developing scalable, economically viable and socio-environmental EES technologies are discussed. The paper explores EES's evolving roles and challenges in power system decarbonization and provides useful information and guidance on EES for further R&D, storage market building and policy making in the transition to zero-carbon power systems.

The efficiency of solar photovoltaic (PV) panels is greatly reduced by panel soiling and high temperatures. A mechanism for eliminating both of these sources of inefficiencies is presented by integrating solar PV generation with a compressed air system. High-pressure air can be stored and used to blow over the surface of PV panels, removing present dust and cooling the panels, increasing output power. A full-system mathematical model of the proposed system is presented, comprised of compressed air generation and storage, panel temperature, panel cleaning, and PV power generation. Simulation results indicate the benefit of employing compressed air for cleaning and cooling solar PV panels. For a fixed volume of compressed air, it is advantageous to blow air over the panels early in the day if the panel is soiled or when solar radiation is most abundant with the highest achievable flow rate if the panel is clean. These strategies have been shown to achieve the greatest energy captures for a single PV panel. When comparing the energy for air compression to the energy gain from cleaning a single PV over a two-week period, an energy ROI of 23.8 is determined. The system has the potential to eliminate the requirement for additional manual cleaning of solar PV panels.