• Energy Research

AbstractThis paper presents a methodology to predict the optical performance and physical topography of the glass collector surfaces of any given CSP plant in the presence of sand and dust storms, providing that local climate conditions are known and representative sand and dust particles samples are available. Using existing meteorological data for a defined CSP plant in Egypt, plus sand and dust samples from two desert locations in Libya, we describe how to derive air speed, duration, and sand concentrations to use within the Global CSP Laboratory sand erosion simulation rig at Cranfield University. This then allows us to predict the optical performance of parabolic trough collector glass after an extended period by the use of accelerated ageing. However the behavior of particles in sandstorms is complex and has prompted a theoretical analysis of sand particle dynamics which is also described in this paper.

We describe the design of a small thermal desalination unit for use in refugee camps or in emergency situations that might be found after natural disasters. The thermal evaporation and condenser stages are separated for higher efficiency and the process is powered by low-cost PMMA concentrating Fresnel lenses. The overall concept is explained, and the detailed design is presented. The durability of the PMMA lenses is discussed. The design is calculated to produce up to 100 litres of fresh water per day in MENA regions with DNI>700 W/m2 over 8 hours, assuming 50% efficiency. Two manufactured prototypes are to be built in Israel and deployed in Palestine and Jordan for field testing.

The work here involves designing a solar solution for safe cooking and low-power generation intended for application in rural communities. A system was developed that combines Concentrated Solar Power (CSP) and Thermoelectric Generator (TEG) technologies. The CSP provides heat for clean cooking, and the excess heat is harvested by the TEG and converted into electrical power. A storage tank was integrated into the system, storing excess energy and serving as the medium for indirect cooking and supplying the heat required by the TEG. The Parabolic Trough Collector, having a resulting average thermal efficiency value of 21%, provided the useful energy to store over 4.25kWh of heat in the tank during the initial testing of the system. The TEG developed has four Peltier modules and attained 23W - over 80% of their rated power and a maximum conversion efficiency of 4.14% at a temperature difference of 220°C between the cold and hot surfaces of the generator. During the experiment, the TEG operation was limited to only four hours before subjecting a no-load test to assess the total energy storable from the system. The initial results from the test carried out here show the potential of the hybrid system in storing energy in the tank for an extended period and simultaneous operation of the TEG. Excess energy stored can be utilised further in providing the heat required for cooking or further electrical power generation.

The research introduces an innovative approach to enhancing the efficiency of Multi-tower Concentrated Solar Power (CSP) through a configuration termed Auxiliary Tower with Subfield (ATS). ATS introduces an auxiliary tower and creates a subfield by adding heliostats near its position, aiming to optimize the solar field's optical efficiency and offer modular decentralized power output. ATS configuration employs existing field configurations to pinpoint inefficiencies where an additional tower can be installed, and heliostats are systematically added to the subfields through numerical optimization using various design variables. Although the inclusion of a subfield in the ATS configuration enhances energy output, it does not always offset the additional costs of the auxiliary tower, receiver, and extra heliostats, in small fields. However, when applied to larger fields, starting from 200MWth, ATS begins to provide a lower Levelized Cost of Heat (LCOH) compared to optimized conventional thermal fields, demonstrating its potential applicability and efficiency in larger-scale CSP setups. Applying ATS to a 120 MWth Gemasolar-like plant further confirms its advantages, with 160 MWth emerging as the optimal enhancement point that boosted efficiency while lowering LCOH. ATS shows promise as an efficient, modular approach to scaling up power tower system.

The growth in energy demand and global concern about the environment has resulted in the drive towards alternative energy sources and consequently this research concerning solar energy harvesting of radiation received at the earth’s surface. Analysis of solar radiation data is an important tool in the accurate designing/sizing of solar Photovoltaic (PV) systems and conducting performance analysis of the system. This paper presents the statistical and economic analysis of solar radiation and climatic data for the development of Solar PV systems in Nigeria. The data for three locations, one from each of the radiation regions in Nigeria were analysed using Minitab 17. The analysis shows that Maiduguri is more viable for solar energy conversion system than the two other locations, and for the same energy demand of 1.1MWh, the peak watt (Wp) of solar PV array required are 619419.27 Wp, 821142.52 Wp and 1219489.32 Wp for Maiduguri, Minna and Port Harcourt respectively. This leads to a difference of $460,984.72 in the total project cost between Maiduguri and Minna for the same energy demand. Keywords: Analysis, Energy, Environment, Data, Nigeria, PV system

Abstract Linear concentrating solar thermal systems offer a promising method for harvesting solar energy. In this paper, a model for a novel linear Fresnel lens collector with dual-axis tracking capability is presented. The main objective is to determine the performance curve of this technology by means of both experiment and theoretical analysis. A mathematical model including the optical model of the concentrator and the heat transfer model of the receiver pipe was developed. This tool was validated with experimental data collected using a proof of concept prototype installed in Bourne, UK. The performance curve of the collector was derived for temperatures between 40 °C and 90 °C. The results show that the global efficiency of the collector is limited to less than 20%. The energy losses have been analysed. The optical losses in the lens system accounts for 47% of the total energy dissipated. These are due to absorption, reflection and diffraction in the Fresnel lenses. Furthermore manufacturing error in the lens fabrication has to be considered. One third of the solar radiation collected is lost due to the low solar absorptance of the receiver pipe. Thermal radiation and convection accounts for 6% of the total as relatively low temperatures (up to 90 °C) are involved. In order to increase the performance of the system, it is recommended to install an evacuated receiver and to insulate the recirculation system. Considering data from manufacturers, these improvements could increase the global efficiency up to 55%. Utilising the results from this work, there is the intention of building an improved version of this prototype and to conduct further tests.

Abstract Integration of Hydrothermal Liquefaction (HTL) of microalgae biomass with concentrated solar power thermal processing (CSP) for bio-oil production is a potential processing pathway for energy efficient generation of renewable biofuels. Solar HTL infrastructure avoids additional bolt-on components of conventional solar parabolic trough systems used for electricity production including heat transfer fluids, counter current heat exchangers, fluid transfer interconnectivity and electrical power control systems. The absence of such capital intensive additional equipment considerably reduces the production costs of solar HTL biofuels compared to electricity generation from conventional CSP power systems. An economic and market appraisal of variance and system economic resilience is presented. It is hypothesised that the combination of nutrient recycling with HTL/CSP unification has the potential for economically sustainable microalgae bio-oil production. A microalgae biofuel minimum fuel sales price of $1.23/kg has been modelled. Further experimental work would be able to validate this integrated model.

Abstract Ferrofluids containing nanoparticles of Mn 0.5 Zn 0.5 Fe 2 O 4 (MZ5) and Fe 3 O 4 (magnetite) have been examined as potential thermal transport media and energy harvesting materials. The ferrofluids were synthesized by chemical co-precipitation and characterized by EDX to determine composition and by TEM to determine particle size and agglomeration. A range of particle coatings and carrier fluids were used to complete the fluid preparation. Commercially available ferrofluids were tested in custom built rigs to demonstrate both thermal pumping (for waste heat removal applications) and power induction (for power conversion and energy harvesting applications). The results indicate that simple ferrofluids possess the necessary properties to remove waste heat, either into thermal storage or for conversion to electrical power.