Field layout and dispatch optimisation strategies for a concentrating solar thermal plant providing high-temperature process heat
Date
2021-03
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The world is moving towards a more environmentally sustainable future. To achieve this energy intensive sectors must transition to sustainable, alternative energy sources. The high-temperature industrial process heat sector relies heavily on fossil fuel combustion for their energy needs. A potential sustainable alternative to this is concentrating solar technologies, which have proven capabilities of providing high-temperature energy without the emission of Green House Gases. In this thesis concentrating solar technologies are investigated for application in the high-temperature industrial process heat sector. Next generation concentrating solar technology utilising ceramic particles as the heat transfer medium and a central receiver reflector system, are capable of reaching temperatures in excess of 1 000◦C. In this thesis, these technologies are investigated around the concept of a concentrating solar plant providing high-temperature process heat for Manganese ore pre-heating, prior to smelting.
In order to evaluate the concept an optical, energy and economic model is developed forthe concentrating solar plant. From these models, optimisation studies are performed to determine optimal plant operation and heliostat field layouts, to design a plant which provides the required heat at lowest cost. The plant utilises electric backup heaters to ensure a steady heat supply to the ore pre-heater. This occurs in the context of a time-of-use electric tariff. The plant’s operating strategy is determined using an optimal thermal energy storage dispatch profile which ensures backup electric heat is purchased for least cost. It is shown that the optimal dispatch profile reduces the cost of the plant’s supplied heat from 43.03$/MWhthto 37.96$/MWhth, compared to an heuristic strategy. Anovel heliostat technology, the HelioPod which has six heliostats fixed on a commonbase structure, is used in this work. This technology has not been extensively studied for application in the large field sizes required for this work. An optimisation study of HelioPod field layouts is undertaken to determine how to design the field layout to deliver the required energy with the lowest number of heliostats. This work adapts the existing optimised field layout knowledge from literature, based on individual heliostat fields, to pod fields. It was found that the plant’s tower height significantly influences the field design. For a shorter tower height a more sophisticated layout is required to reduce blocking and shading optical losses. For this shorter tower the optimised HelioPod field layout developed improved the plant’s economic performance by 11.18 % compared to an heuristic layout.
A case study for a Manganese smelter with concentrating solar derived process heat for ore pre-heating was developed. The case study investigated a smelter located in the Northern Cape of South Africa. The region has world class solar resource, as well as the largest land based Manganese ore reserves in the world. The concentrating solar plant in this case study was capable of providing process heat at lower cost than diesel combustion, but at nearly double the cost of coal combustion. However if the current trend for concentrating solar cost reduction continues, the technology could reach cost parity with coal in the future.
AFRIKAANSE OPSOMMING: Raadpleeg teks vir opsomming
AFRIKAANSE OPSOMMING: Raadpleeg teks vir opsomming
Description
Thesis (MEng)--Stellenbosch University, 2021.
Keywords
Solar thermal energy, Optimisation . . ., Heaters, Process, UCTD, Renewable energy sources