Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Space heating and cooling, as required for chicken poultry farming, is an energy intensive operation. Due to the continuous rise in the prices of fossil fuel, water and electricity, there is a need to develop renewable and sustainable energy systems that minimise the use of fuel or electricity, for heating, and water, for cooling of air. The HYDROSOL (HYDro ROck SOLar) system, developed at Stellenbosch University, is such a renewable energy system that potentially provides a low cost solution. Instead of using conventional gas and electricity heaters for the heating of air during winter, the HYDROSOL system collects solar heat, stores it in a packed bed of rocks and dispatches the heat as required. During hot summer days, when cooling is needed, the rocks are cooled during the night when the ambient temperatures are low and/ or by evaporative cooling by spraying water onto them. During the day, hot air is then cooled when it passes through the colder rocks with minimal water consumption compared to current systems. In this thesis, a prototype of the HYDROSOL system is presented, designed and built for experimental testing. A transient 2-D thermo flow model is developed and presented for the analytical and experimental performance evaluation of this system for solar heating and night air cooling operation. This model is used to conduct a parametric study on HYDROSOL to gain a better understanding of the operation and control of the system. The HYDROSOL concept is intended to be used for heating and cooling of residential buildings, office suites, warehouses, shopping centres, food processing industries e.g. drying of foods, and various agricultural industries e.g. greenhouses. In this thesis, a HYDROSOL system is developed mainly for poultry broiler houses in South Africa focussing on convective dry cooling, charging the rock bed with night-time ambient air, and convective heating, harvesting solar heat during the day, with different modes of operation available. / AFRIKAANSE OPSOMMING: Ruimte verhitting en verkoeling, soos benodig vir hoender pluimvee boerdery, is ‘n energie intensiewe bedryf. As gevolg van die voortdurende styging in fossiel brandstof-, water- en elektrisiteitpryse, het ‘n behoefte ontstaan om hernubare en volhoubare energie-stelsels te ontwikkel wat minder brandstof of elektrisiteit, vir verhitting, en water, vir verkoeling van lug, gebruik. Die HYDROSOL (HYDro ROck SOLar) stelsel, wat ontwikkel is by die Universiteit van Stellenbosch, is ‘n hernubare energie-stelsel wat ‘n potensiële lae koste oplossing bied. In plaas daarvan om konvensionele gas en elektrisiteit verwarmers vir verhitting van lug gedurende die winter te gebruik, maak HYDROSOL gebruik van son warmte, stoor dit in `n gepakte bed van klip en onttrek die warmte soos benodig. Gedurende die warm somer dae wanneer verkoeling benodig word, word die klippe gedurende die nag, met kouer omgewings lug en/of met verdampingsverkoeling, deur water op die klippe te spuit, afgekoel. Gedurende die dag word warm lug afgekoel deur die lug oor die koue klippe te forseer met minimale waterverbruik in vergelyking met huidige stelsels. ‘n Prototipe van die HYDROSOL word voorgestel, ontwerp en gebou vir eksperimentele doeleindes. ‘n 2-D tyd afhanklike termo- vloei model word voorgestel vir die analitiese en eksperimentele verrigting evaluering vir son verhitting en nag lug verkoeling. Hierdie model word gebruik om ‘n parametriese studie te doen om die werking en beheer van HYDROSOL beter te verstaan. Die HYDROSOL stelsel is bedoel om die verwarming en verkoeling vereistes van residensiële geboue, kantoor areas, pakhuise, winkelsentrums, voedsel verwerking nywerhede, soos bv. die droging van voedsel, en verskeie landboubedrywe, soos bv. kweekhuise, te bevredig. In hierdie tesis word ‘n HYDROSOL stelsel, hoofsaaklik vir pluimvee kuikenhuise in Suid- Afrika, ondersoek en fokus op die droë verkoeling, deur die rotsbed te laai gedurende die nag, asook droë- verhitting, wat gebruik maak van son energie gedurende die dag en kan beheer word op verskillende maniere.

The aim of this thesis is to develop a new business model for district heating and cooling firms which can contribute to a stabilization of the Swedish national energy system. The business model is developed for a district heating and cooling firm and is exemplified with Fortum Heat. The theoretical investigation around the topic creates a rigid base for following qualitative empirical studies. Osterwalder’s canvas for business model generation is used together with a Casual Loop Diagram to identify a number of business opportunities which stabilizes the national energy system. One of the business opportunities is developed into a business model. The study results in a business model which offers Svenska Kraftnät an increased volume of electricity production through free capacity in CHP plants. This stabilizes the national energy system when the electricity production from renewable energy sources is low. Free capacity occurs due to more and more energy efficient buildings and investments in new production capacity. Heat from the electricity production is loaded into thermal storages to cover a part of the future need for heat. Heat can also be rejected as surplus heat into water if the demand for electricity is high. Renewable biofuels turn CHP plants into bio-condensing electricity power plants. A general exemplification of this situation at Fortum Heat shows positive economical results. Producing electricity independently of the current demand of heat makes it possible for Fortum Heat to be a part of Svenska Kraftnät commercialization of the power reserve. A finalizing discussion highlights aspects needed to be considered when implementing the business model at Fortum Heat.

This study presents a Techno-economic assessment of a renewables based power generation project for PS 21, a Pumping Station for Kenya Pipeline Company located in Nairobi, Kenya. The load for the pumping station is 1135 kW Continuous. The assessment criteria used was levelized cost of energy. The hybrid renewable energy system software HOMER was used for assessment, and modeling was done using hourly TMY data for solar irradiance and wind.  According to the results, Hybrid Solar PV-Wind- Battery renewable energy systems can supply adequate power for pumping station purposes. Optimization modeling at 2010 prices gave a levelized cost of energy of $0.2 per kWh for the most optimal solution which consisted of 2 No. 1650 kW Vestas V 82 Wind Turbines and 4070 kW of PV modules. This cost of energy just matches the purchase price from the National grid which varies between $0.14 and $0.2 per kWh, and therefore, the project is economically feasible. Mainly due to concerns of global warming, the view in the Kenyan government and society towards renewable energy is very favorable and  the project is also politically and socially feasible.   Sensitivity analysis demonstrated that wind energy is more viable than solar PV energy in areas of high wind speeds, with about 7.5 m/s annual average wind speeds.   The results show that the levelised cost of energy may be significantly decreased in future due to the fact that the cost of PV modules is progressively reducing. Payments for CERs under CDM mechanism of the Kyoto Protocol would lower the levelised cost of energy further. The Project was found to be feasible. / <p>I was a distance student and did the presentation online via centra.</p>

The question how a least-cost spatial allocation of sustainable electricity infrastructure may look like using different decision-making procedures (markets, different kinds of land-use and grid regulations) has not yet been analysed explicitly. We measure the sustainability of emerging energy landscapes providing power from renewable energy sources (RES) by an overall welfare function also comprising all kinds of space-related disutilities, i.e. spatial externalities - be they site-specific or related to the distance to a residential area (consumer centre). The presented agent-based model (ABM) concept aims at assessing different policy scenarios to govern the land-use for energetic purposes under the constraint of ensuring the electricity supply for a virtual landscape with RES. To derive optimal spatial allocation an agent-based modelling approach is implemented, which includes a virtual landscape, three settlements as demand centres and profit-oriented producers of renewable power. For the design of the electricity grid and the calculation of grid-related reinforcement costs a load-flow model is applied, being also able to map grid externalities during the RES expansion in space. The model allows RES producers to choose profit-maximising cells for plant installations until the given demand for power of the virtual landscape is met. Different policy scenarios allocate particular costs to agents (e.g. grid reinforcement costs, spatial externalities) or restrict the land-use with respect to ecological or social restraints. Furthermore, consumer centres have the possibility to follow own particular regional strategies, to increase their individual benefit. The overall efficiency of allocation (total cost level) as well as the distributional fairness (regional net costs) are evaluated for the policy scenarios and the regional strategies.

This paper examines the possibility of adding a photovoltaic(PV) power station to an already planned wind park in terms of profitability. At this time, southern Sweden’s grid is facing a number of challenges and is hurting economic development. Hybrid parks have showed to be able to tackle some of those challenges. This study has used a two-scaled methodology to analyse which solar PV size is the optimal to be co-located to the wind park of 24MW[Office1] . The results show that the 21MW size is the ideal one. In addition, to complement the findings, an analysis has been conducted to determine which battery size would be the optimal size to be added to the hybrid system. The results showed that a 1MW/1MWh battery storage would be the ideal size, however, it is possible that a 5MW/MWh battery storage might produce better results if peak shaving is included. All the scenarios in this study have been analysed in terms of IRR.

The UK domestic sector accounts for more than a quarter of total energy use. This energy use can be reduced through more efficient building operations. The energy efficiency can be improved through better control of heating in houses, which account for a large portion of total energy consumption. The energy consumption can be lowered by using renewable energy systems, which will also help the UK government to meet its targets towards reduction in carbon emissions and generation of clean energy. Building control has gained considerable interest from researchers and much improved ways of control strategies for heating and hot water systems have been investigated. This intensified research is because heating systems represent a significant share of our primary energy consumption to meet thermal comfort and indoor air quality criteria. Advances in computing control and research in advanced control theory have made it possible to implement advanced controllers in building control applications. Heating control system is a difficult problem because of the non-linearities in the system and the wide range of operating conditions under which the system must function. A model of a two zone building was developed in this research to assess the performance of different control strategies. Two conventional (On-Off and proportional integral controllers) and one advanced control strategies (model predictive controller) were applied to a solar heating system combined with a heat pump. The building was modelled by using a lumped approach and different methods were deployed to obtain a suitable model for an air source heat pump. The control objectives were to reduce electricity costs by optimizing the operation of the heat pump, integrating the available solar energy, shifting electricity consumption to the cheaper night-time tariff and providing better thermal comfort to the occupants. Different climatic conditions were simulated to test the mentioned controllers. Both on-off and PI controllers were able to maintain the tank and room temperatures to the desired set-point temperatures however they did not make use of night-time electricity. PI controller and Model Predictive Controller (MPC) based on thermal comfort are developed in this thesis. Predicted mean vote (PMV) was used for controlling purposes and it was modelled by using room air and radiant temperatures as the varying parameters while assuming other parameters as constants. The MPC dealt well with the disturbances and occupancy patterns. Heat energy was also stored into the fabric by using lower night-time electricity tariffs. This research also investigated the issue of model mismatch and its effect on the prediction results of MPC. MPC performed well when there was no mismatch in the MPC model and simulation model but it struggled when there was a mismatch. A genetic algorithm (GA) known as a non-dominated sorting genetic algorithm (NSGA II) was used to solve two different objective functions, and the mixed objective from the application domain led to slightly superior results. Overall results showed that the MPC performed best by providing better thermal comfort, consuming less electric energy and making better use of cheap night-time electricity by load shifting and storing heat energy in the heating tank. The energy cost was reduced after using the model predictive controller.

Wind resources are highly intermittent and fluctuant, making wind turbines less reliable and the unstable power output will affect grid stability and security. This paper presents an idea of integrating the solar PV plant and energy storage system into an existing wind project, project Rödene in Gothenburg. The hybrid renewable system, which consists of two or more renewable energy sources, is considered the renewable energy development trend. An economic analysis of a 1.2 MW PV plant, 5 MW lithium-ion battery storage system and 300 kg hydrogen fuel cell storge system are assessed in terms of LCOE and LCOS of plants. The revenue stream is discussed separately, consisting of electricity tariff, ancillary services and energy arbitrage. The results show that both PV plant and energy store systems are unprofitable. When the PV panel cost is reduced more than 30% and the annual production increases at least 30%, the LCOE of the PV plant arrives at the break-even point. Also result shows the hydrogen fuel cell energy storage system is too expensive of commercial use, and the battery energy storage system has a high potential of profitable if the ancillary service in Sweden is well organized in the future

Indiana University-Purdue University Indianapolis (IUPUI) / With the increasing demand of economy and environmental pollutions, more and more renewable energy systems with clean sources appear and have attracted attention of systems involving solar power, wind power and hybrid new energy powers[1]. However, there are some difficulties associated with combined utilization of solar and wind, such as their intermittent behavior and their peak hours mismatch in generation and consumption[1]. For this purpose, advanced network of a variety of renewable energy systems along with controllable load and storage units have been introduced[1-3]. This thesis proposes some configurations of hybrid energy harvesting systems, including wind-wind-storage DC power system with BOOST converters, solar-solar-storage DC power system with cascade BOOST converters, wind-solar-storage DC power system with BOOST converter and cascade BOOST converter, and wind-solar DC power system with SEPIC converter and BOOST converter. The models of all kinds of systems are built in Matlab/Simulink and the mathematical state-space models of combined renewable energy systems are also established. Several MPPT control strategies are introduced and designed to maximize the simultaneous power capturing from wind and solar, such as Perturb & Observe (P&O) algorithm for solar and wind, Tip Speed Ratio (TSR) control and Power Signal Feedback (PSF) control for wind, and Sliding Mode Extremum Seeking Control (SM-ESC) for wind and solar systems[4]. The control effects of some of these MPPT methods are also compared and analyzed. The supervisory control strategies corresponding to each configurations are also discussed and implemented to maximize the simultaneous energy harvesting from both renewable sources and balance the energy between the sources, battery and the load[2]. Different contingencies are considered and categorized according to the power generation available at each renewable source and the state of charge in the battery[2]. Applying the system architectures and control methods in the proposed hybrid new energy systems is a novel and significant attempt, which can be more general in the practical applications. Simulation results demonstrate accurate operation of the supervisory controller and functionality of the maximum power point tracking algorithm in each operating condition both for solar and for wind power[3]

Yes / The cost of electricity produced by thermal power plants in Republic of Djibouti is relatively high at about $0.32/ kWh. This is due to its dependence on imported oil coupled with fluctuating oil prices. Consequently, the customer pays a high electricity bill. However, Djibouti is endowed with indigenous renewable energy resources such as a good solar irradiance of 5.92 kWh/ m2 day, a potential geothermal energy estimated up to 1000 MW, and few sites with annual wind speed higher than 6 m/s. The goal of this paper is, therefore, to assess an economic evaluation of different grid connected hybrid renewable energy systems to a residential urban house located in Tadjourah city (11.7913◦ N, 42.8796◦ E) in the North-Eastern part of Djibouti to reduce the cost of electricity from the grid. To reach this objective, a powerful software tool called HOMER (Hybrid Optimization Model for Electric Renewables) has been used to find the optimum hybrid energy system using real wind and solar irradiation data. The results obtained from this study show that the best economical suited combination of hybrid renewable energy system is a PV-Wind grid connected system. This study shows also that potentially the indigenous renewable energy contribution, in Tadjourah, can be as much as 77 % with 47 % of solar and 30% of Wind energy. The Net Present Cost, the Levelized Cost of Energy, and the operating cost of the optimal HRES are $337, $0.002/kWh and $1,025/year, respectively. When compared with the average cost of grid-only connection of $0.32/kWh, the optimal hybrid renewable energy system is more economical and will save 51 % of the cost that the customer must pay when using only the electricity from the grid.

Urban areas house most of the global population and are also responsible for large shares of global greenhouse gas emissions. Cities and municipalities thus play a significant role in modern society to achieve an energy transition to renewable energy sources and to adapt to climate change. Achieving such a transition is a difficult process due to the high energy density and complexity of urban multi-energy systems. This is further exacerbated by the adverse effect future climate hazards will likely have on urban infrastructure. Despite this, energy development and climate adaptation plans are often researched and drafted in a disjointed manner. In many instances, future energy strategies do not consider climate impacts, whereas climate adaptation tactics disregard energy production. This study proposed that such mutually exclusive analysis and decision-making increases the vulnerability of planned and optimised future urban energy systems. Investigating the Swedish municipality Malmö, the study focused on achieving a future energy transition in its electricity network and then considering potential climate change impacts. Current urban energy plans and capacity were used to forecast the renewable energy potential for 2030 in Malmö’s geographical area. This formed the basis for modelling an optimised hybrid renewable energy system for the municipality using HOMER Grid. Based on future climate data and Malmö’s climate adaptation plans, this system was then evaluated in terms of impacts from climate hazards. The results indicated that Malmö’s current energy plans would expose a large share of their energy infrastructure to risk of damage from climate hazards. Thus, the vulnerability of the optimised energy system is indeed heightened when disregarding climate change impacts in the planning phase. If climate change and energy transition strategies are developed conjointly, urban energy system resilience could likely be increased significantly.