In October 2024 CESET team member Dawit Habtu Gebremeskel, Addis Ababa Institute of Technology, Addis Ababa University, Ethiopia gave a conference presentation entitled "Effective strategies for wind power integration in the context of dominant hydropower-case of Ethiopia" at the 2024 NAWEA/WindTech Conference, New Jersey, USA with the financial support of the CESET conference. Below is a blog on the content of the presentation.
Hydropower is the dominant source of Ethiopia’s power generation accounting for over 90% of its electricity production. Heavy reliance on hydro has left Ethiopia’s power sector vulnerable to dry years due to drought and climate change impacts. This has resulted in severe power cuts due to falling reservoir levels of large hydropower plants. In response, the government has started to diversify the country’s energy mix with variable renewable resources – mainly wind energy. However, diversification of the power mix cannot be the only strategy to efficiently manage the dry-year challenge. The purpose of this paper is therefore to draw and investigate effective strategies for synergistic operation of wind and hydropower systems in Ethiopia so that the country can parallelly address wind integration impacts and take advantage of the techno-economic opportunity for its renewable resources.
The document called “Transforming our world: the 2030 Agenda for Sustainable Development” was adopted at the United Nations (UN) Sustainable Development Summit in New York in September 2015. It set the official launch of the 17 Sustainable Development Goals (SDGs). With the Goal-7 “Ensure access to affordable, reliable, sustainable and modern energy for all”, the agenda 2030 aims to substantially increase the share of renewable energy in the global energy mix and ensure universal electricity access in developing countries. As a result, spurred on by ambitious national commitments, international agreements and rapid technological progress, national governments are increasingly choosing renewable energy to expand their power infrastructure. Renewables provided 28% of power generation worldwide by 2020. With the rapid adoption of more ambitious plans and policies, this could reach 45% by 2030. Until recently, hydropower remained by far the largest source of renewable power globally, followed by wind and solar PV. However, at the end of 2023, solar accounted for the largest share of the global total and with an increase of 116 GW in 2023, growth in wind power has seen its biggest increase in the past decade.
Amid this global transition towards a dominated renewable power, the integration of wind energy presents new challenges to utilities and power system operators in dealing with resource variability and uncertainty. Variability and uncertainty have always been common characteristics of conventional power systems which are managed by grid operators with reserves and flexible generation through dispatchable generators by adjusting their output to follow demand. Emerging innovations have focused on increasing flexibility not only on the supply side but also to all segments of the power system, including grids and the demand side to integrate and effectively manage large-scale variable renewable energy (VRE). Many research papers published to date have also dealt with various measures and flexibility solutions to manage variations. However, it is important to note that the right mix and the best solutions may be different for each country with unique system contexts. Consequently, in line with the global goals and local needs, this work presented in this paper adds to the previous variation management strategies by investigating combined strategies tailored to the Ethiopian context with dominant hydropower generation.
Ethiopia is one of the most suitable nations in Africa for tapping renewable energy resources. Ethiopia currently has an installed capacity of 5,200MW, with potential to generate over 60,000 Megawatts of electric power from hydropower, solar and wind in addition to geothermal and bioenergy as alternative source. Historically, hydropower generation has been the dominant source that today accounts for over 90% of electricity production. Heavy reliance on hydro leaves Ethiopia’s power sector vulnerable to dry years due to drought and climate change impacts. The country has faced insufficient generation due to falling reservoir levels in previous years that forced severe power cuts and rotational load shedding (e.g. six months in 2003 and two months in 2008). The low water levels could likely become more frequent and pronounced in the future considering severe climate change impacts and increased evaporation rates. Knowing this, the government of Ethiopia has a plan to diversify the country’s energy mix with wind, solar and geothermal resources to create a low-carbon future and complement the large-base of hydro. However, diversification of the power mix can not be the only strategy to effectively manage the dry-year challenge. Smooth and effective integration of variable renewables needs to draw on a portfolio of solutions, including generation, interconnections, transmission and distribution, storage, demand-side management, and distributed/community-owned energy systems. System characteristics of a specific country also influences the appropriate combination of solutions and for Ethiopia, various effective flexibility measures can be combined and optimised to reduce costs and maxmise system benefits. These applicable strategies are shown in Figure 01 below.
Figure 1. Flexibility options and effective variation management strategies for Ethiopia.
Use of variable energy resources such as wind results in additional variability and uncertainty for the hydro-dominated Ethiopian power system. On the other hand, hydroelectric generation has been well documented as a flexible and fast-responding resource, which can be quite complementary to variable and uncertain wind resources. The value and benefits of energy from hydropower are higher during extended dry periods and lower during extreme wet periods. Accordingly, because of the potential for synergistic operation of wind and hydropower facilities, the country can investigate the opportunity to integrate wind and hydropower systems by optimizing their output through coordinated operation. In addition, the government’s plan of diversification by wind can further be enhanced by accounting the spatial and temporal differences in the relationship between wind speed and reservoir inflow behavior during wind farm site selection.
Forecast accuracy is important as it is one of the largest factors used to determine the amount of reserve power (spinning reserves, standby reserves) required at any given time during the day. In this regard, Ethiopia should utilize the ability to predict wind farm outputs by making accurate weather forecasts from meteorological information. Another effective way to manage the hydro-wind integrated power supply systems is the use of back-pumped reservoirs to complement the critical times of the hydrological inflows and the periods of low wind speeds. The pumped hydro-storage system can be applied to selected hydropower station/s considering the reservoir size, spatial and temporal availability of hydrological inflows and wind speeds. The pumped hydro-storage system can also be powered by wind turbines that pump water from the lower reservoir to the upper reservoir in order to supply reliable and steady water to the hydro-turbines.
Other strategies that are applicable for the context of Ethiopia include a combination of 1) integrating dispatchable generation like national fuel-based generation (e.g. natural gas based combined cycle), 2) regional balancing with export/import of electricity with neighboring countries, 3) introducing grid storage systems, 4) distributed/community owned energy systems – use of such systems can provide several benefits to the network, including alleviating congestion, reducing transmission losses, providing ancillary services and reserve requirements as a substitute of conventional power plants and, 5) implementing demand-side management and electric-vehicle smart charging.
