• Energy Research

Thesis (PhD) -- Stellenbosch University, 2022. ; ENGLISH ABSTRACT: As its first novel contribution, this dissertation investigates the broad challenge of understanding the impacts of integrating a high share of variable renewable energy (VRE) generators into power systems. These generators are variable, uncertain, non-synchronous and location constrained, introducing a wide range of impacts that are unique to a specific region and require different input data, models, and simulation tools to study. It is resource intensive to study all these impacts and therefore important to effectively identify and study only those impacts that are most relevant to the region under consideration. In addressing this challenge, this dissertation firstly identifies three main factors that influence the VRE integration impacts in different regions: available resources, penetration level, and grid characteristics. Thereafter, the international experience is used to understand how these three factors contributed to the issues that were experienced in different regions. The outcome of this investigation is a framework for comprehending VRE integration issues based on available renewable resources, penetration level, and grid characteristics of a region under consideration. This framework can be used by network planners, policymakers, and grid operators to prioritize VRE integration issues of concern to their region prior to conducting detailed studies, thereby reducing the resources required. This dissertation identifies wind power forecasting as key in mitigating some of the impacts introduced by high share of VREs. Within the context of wind power forecasting, this dissertation investigates the challenge of aggregating decentralized forecasts. These forecasts are typically optimized for local conditions because the individual wind farms do not have access to power data from other wind farms. Simply adding these decentralized forecasts together at the point where these forecasts are received (typically the system operator) may not ...

As part of work package nº2 of the H2020 PROSEU project, which aimed to establish a baseline review and characterisation of renewable energy sources (RES) prosumer (self-consumption) initiatives across Europe, databases identifying the diversity of collective forms of RES prosumers and related stakeholders were built by the project partners using the templates and respective variables presented here (English language). The databases served to create a stratified sample of RES prosumer initiatives for purposes of a survey, as well as distinguish them from other stakeholders in the field. H2020 project PROSEU - Prosumers for the Energy Union: Mainstreaming active participation of citizens in the energy transition. Work package 2 (WP2) - Baseline analysis and Characterization of RE Prosumer Initiatives

In order to integrate more and more variable renewable energy sources (VRES) electric grids play a significant role. There is an obvious need for more interconnections and more enhanced grids with more VRES. On the other side, the monetary, material, social and spatial constraints (free corridors) impose limits on grid expansions. Robust modelling of electric grids (distribution, transmission and interconnection) at World level in integrated assessment models (IAMs) is beyond the state of the art of current computation capabilities and data availability. A number of relevant input data like length of the grids, voltage levels, rated power, and after that material prices, population density, VRES shares of generation and flexibility technologies, hourly curtailments in the energy system are not sufficient to calculate explicit limitations imposed by power flows. Therefore, the idea of this paper is that in the absence of sufficient data and computability, for the first time some expert assumptions in the form of proportions are used to represent interconnection grids as an important constraint and flexibility option for variable renewable energy production, modelled at hourly level during one year using EnergyPLAN. These assumptions are about proportions of newly integrated renewable energy between transmission and distribution grids, proportions of grids to the generation plants and their utilization. Suggested method for application in WILIAM will be illustrated.

As part of work package nº2 of the H2020 PROSEU project, which aimed to establish a baseline review and characterisation of renewable energy sources (RES) prosumer (self-consumption) initiatives across Europe, databases identifying the diversity of collective forms of RES prosumers and related stakeholders were built by the project partners using the templates and respective variables presented here (English language). The databases served to create a stratified sample of RES prosumer initiatives for purposes of a survey, as well as distinguish them from other stakeholders in the field. H2020 project PROSEU - Prosumers for the Energy Union: Mainstreaming active participation of citizens in the energy transition. Work package 2 (WP2) - Baseline analysis and Characterization of RE Prosumer Initiatives

The concept of renewable energy sources complementarity has attracted the attention of researchers across the globe over recent years. Studies have been published regularly with focuses on aspects such as new metrics for complementarity assessment, the optimal operation of hybrid power systems based on variable renewables, or mapping resources complementarity in a specific region. This study targets the present literature gap, namely a lack of complementarity study covering explicitly the whole World, based on the same data source and methodology. The research employs Kendall’s Tau correlation as the complementarity metric between global solar and wind resources and a pair of indicators such as the solar share and a sizing coefficient usually applied in the domain of hybrid generators. This method allows to conduct a preliminary estimation of a solar and wind energy hybrid generator based on a daily demand of 1 kWh. The data series employed in this study come from NASA’s POWER Project Program, covering the years 2001–2020. This work provides an interesting insight into the global variability of the complementarity between these two variable energy sources. Significant findings of this paper include that Kendall’s Tau ranges between –0.75 and 0.75, in line with previous research for specific regions, thus providing a theoretical maximum for planning. Additionally, the results suggest that in most tropical and subtropical areas, the hybrid solar-wind generator should be dominated by the solar portion to minimize the variability of the total daily energy produced.

This study was commissioned to support the government of Pakistan, the provincial energy departments, and the electricity regulator in the implementation of competitive bidding for the procurement and development of all future variable renewable energy (VRE) capacity in the country. The decision was taken in 2017 to move from a “cost-plus” tariff-setting regime for future solar and wind power capacity to one based on the principles of competitive bidding, following international trends and the very positive results seen in terms of steep cost reductions in other countries. In many locations, these cost reductions have led to solar and wind becoming the “least-cost” form of power generation, although this has already been achieved in Pakistan through gradual declines in the tariff awarded on a cost-plus basis to solar and wind projects by NEPRA, the electricity regulator. The report is structured as follows: Section 2 outlines key background issues of relevance to competitive bidding mechanisms for RE in Pakistan; Section considers potential arrangements for deployment of competitive bidding; Section 4 analyzes tender governance processes; Section 5 examines detailed arrangements for the design of competitive bidding; Section 6 evaluates implementation arrangements; Section 7 considers the impact of the forthcoming Competitive Trading Bilateral Contract Market (CTBCM) on renewable energy (RE) competitive bidding mechanisms; Section 8 reviews information technology needs; Section 9 considers communications and marketing strategies; and Section 10 reviews the potential for introducing local content arrangements.

A study published by the ISE estimates transmission-related benefits attributable to the geographic diversification of variable renewable generation and loads. The analysis indicates that the benefits of transmission expansion between areas with diverse renewable generation resources are greater than typically estimated, with significant reductions in system-wide costs and renewable generation curtailments in both hourly day-ahead and intra-hour power market operations. The benefits are substantial and yet often not accounted for because they are more difficult to model. The key findings of the study include the following: 1. For renewable generation levels from 10% to 60% of annual energy consumption, interconnecting two power market sub-regions with different wind regimes through transmission investments can reduce annual production costs by between 2% and 23% and annual renewable curtailments by 45% to 90%. 2. When real-time uncertainties of renewable generation and loads relative to their day-ahead forecasts are taken into consideration, the benefit of geographic diversification through the transmission grid are 2 to 20 times higher than benefits typically quantified based only on “perfect forecasts.” The findings of the study highlight the important role transmission expansion can play in successfully integrating large-scale renewable generation under both forecasted day-ahead and real-time market conditions. The authors also emphasize the need for transmission benefit-cost analyses to go beyond deterministic hourly simulations and begin taking into account both forecasting uncertainty and intra-hour system conditions to fully capture the regional and inter-regional renewable generation diversification benefits of the transmission system.

The objective of this study is to identify the most suitable zones for solar and wind power development in Pakistan. The study was carried out by a team of expert consultants over a period of 18 months in collaboration with all the key federal organizations in power system planning, led by the National Transmission and Despatch Company (NTDC) as the primary technical counterpart, with the findings reported to the Ministry of Energy (Power Division). This study confirms that Pakistan has excellent resources for economically viable solar power and wind power generation, both of which are mostly untapped so far. Especially noteworthy is the huge potential in western Balochistan for both solar and wind power, which will require significant grid infrastructure investments to be exploited. Further excellent areas with large solar potential are to be found in Sindh and southern Punjab, and the wind corridors in southern Sindh around Jhimpir and Gharo still have more potential than what has been developed so far.

We propose a new approach for the visual inspection of interactions between several variables related to the wind and solar energy sector, and a set of socioeconomic variables and natural factors that may be affecting the sector. Focusing on fifteen European countries in the period from 2007 to 2019, we use Categorical Principal Component Analysis to reduce our data into two factors, the first relating to energy consumption, greenhouse gas emissions, per capita income, and solar energy, and the second capturing climactic and sociopolitical factors. The dimensionality reduction also displays a decoupling between natural factors and variable renewable energy sources (VRES) development, particularly in the case of solar energy, and instead shows a more influential relationship with economic factors. We additionally project all countries into a perceptual map and observe three clusters that roughly correspond to the main European regions (Southern and Eastern Europe, Northern Europe and Western Europe). Finally, we plot the average level and growth level of both the wind and solar energy share for each nation and observe a negative relationship in wind share and a slightly positive relationship in solar share. Our results show that, especially for wind energy, countries with higher levels of overall renewable energy development are more likely to show more intense VRES development than countries who already have high existing levels of the technology in their renewable energy mix. Solar energy investment on the other hand is more likely to be dominated by countries with pre-existing high levels of solar in the renewables mix. Our results emphasize the importance of individual nations attitude towards renewables as a whole as playing a key role in VRES development, as much as the natural resource availability of these energies.