*3.4. Political Barriers*

Policy measures are of vital importance for large-scale introduction of PV. A lack of stability of incentives for the adoption of PV can be a significant barrier—for instance a sudden removal of existing subsidies or inconsistencies in policy measures.

Kenya has instituted policies meant to increase the integration of PV [1]. Particularly, among these policies is the Kenya Rural Electrification Master Plan [48], a Feed-in Tariff policy [49] and the Vision 2030 [50]. The government has also made a move towards ensuring that entrepreneurs willing to invest in solar PV are catered for [47].

As early as 2008, Kenya developed a feed-in tariff policy meant to ensure market stability for investors in PV. The feed-in tariff made it possible for independent power producers to deliver power from wind and hydro sources to the national grid. In 2012, the feed-in tariff policy was revised to also include solar power [37]. However, these policies have not translated to higher installed grid-connected PV capacity largely because the policies are not well coordinated during implementation or at worst, they are not implemented at all [1].

Under- or over-prioritization of investments in certain sectors in relation to others is usually not based on technical decisions but rather involves political choices and prioritizations. Large-scale PV projects are essentially large infrastructure projects that are typically highly political and that involve a multitude of actors with competing interests and negotiations across various levels. For example, [51] argue that the push for RE in Kenya is not necessarily being driven by environmental concerns, but rather by the need to provide access to electricity to the highest number of people within the shortest time possible. These authors highlight the tensions that come from pursuing the multiple objectives of 'growth', 'inclusiveness' and 'sustainability'.

#### **4. Pumped Hydro Storage Solution**

This section discusses pumped hydro storage solution by reflecting on experiences from various countries which have similar conditions as Kenya. The importance of pumped hydro as a possible solution that can be replicated locally to meet electricity demand can therefore be proven since it has been applied in various countries with similar conditions as Kenya.

The shift from fossil fuel-fired power production to RES such as PV requires some form of storage or flexibility to cope with intermittency of the sources. A limitation with batteries is that they cannot offer multiple-hour storage capacity and discharge over a long time period. Moreover, batteries have a specific lifespan beyond which their performance is not guaranteed. Batteries also require ample housing space for large power output.

Pumped hydro storage (PHS) is a form of energy storage whereby gravitational potential energy of water is pumped from a lower reservoir to a higher one serve as a dispatchable reservoir to feed turbines on request [52]. PHS is the largest form of grid energy storage available; currently, PHS accounts for about 95% of all active and tracked storage [53]. The first PHS systems were commissioned in Alpine Switzerland, Austria and Italy in the 1890's. World-wide installed capacity stands at over 181 GW, of which about 29 GW are in the USA [52].

Modern PHS plants have a cycle efficiency of about 80% [54,55], and allow the utilization of excess electricity from base-load power sources (such as coal or nuclear) or fluctuating RES to be saved for use during periods of higher demand. Reservoirs used in these systems are generally smaller compared to conventional hydroelectric dams of similar power capacity and their generating periods are often less than half a day.

Chile has vast amounts of solar and wind resources which are increasingly being harnessed to replace fossil fuel generation. The impact of large scale integration of these variable RES for grid-level electricity storage was evaluated by [55]. In this study, a cost-based linear optimization of the Chilean electricity system was developed to analyse and optimize various RES generation, transmission and energy storage scenarios until 2050. Results of this study showed that for the base scenario of decommissioning of aging coal plants and no new coal and large hydro generation, the generation gap can be filled by PV, concentrated solar power and flexible gas generation resulting in a drop of 78% in carbon dioxide emissions. Integration of PV for on-grid storage increases the solar PV fraction which consequently leads to a 6% reduction in operation and investment costs by 2050 [55].

Switzerland was a pioneer in electricity generation and a European leader in power storage [56]. The country's mountains, extensive snows and glaciers favour development of hydro technology which is well developed and mature. As a result, hydro power generation from Switzerland is critical in western European electric power system supply backup and means of storage of reserve power [5,55]. Power management and storage are also critical towards achieving 100% renewable energy-based system in Switzerland. The country utilizes two different hydro storage systems; PHS and hydro systems with natural inflows to reservoirs that are subsequently feed to turbines on demand

A steady increase of the RES share in Australia's electricity mix is causing a move away from dependency on fossil fuels. A study by [57] focusing on the South West Interconnected System in Western Australia modelled several high penetration scenarios for renewables comprising wind and PV and PHS. The scenarios were examined using a chronological dispatch model restricting to technologies that were already deployed on a large scale i.e., greater than 150GW were utilized. Results obtained demonstrated that 100% penetration of wind and PV electricity is compatible with a balanced grid—though requiring PHS. Furthermore, with the integration of PHS, a RES share over 90% will still be allowed at a competitive electricity supply cost.

A case study by [58] based on Ometepe island, Nicaragua simulated a PHS and geothermal plant using HOMER software. The island was chosen because it has wind, solar and geothermal resources as well as an extinct volcano with a crater on its top that can serve as the upper reservoir for the PHS system. Different system configurations were demonstrated and the results obtained revealed that PHS technology is able to serve the base load of the system, therefore reducing the required installed capacity of other power resources as well as decreasing the storage requirements and excess electricity production.

Zimbabwe is among the African countries which rely on power imports to meet its energy needs which endangers the energy security of the nation. Several studies have been conducted to assess the feasibility of hybrid power generating systems that incorporate intermittent power sources such as PV with or without storage in order to maximize technical and economic feasibility. One such study by [59] made a techno-economic comparison between standalone wind or PV and hybrid PV/wind. The hybrid system was based on maximizing intermittent energy sources. Results obtained showed that the levelized cost of electricity was less than or equivalent to the local grid tariff. The study further revealed that the utilization of RES would boost energy security and reduce dependency on imported energy.

A 2000 MW PHS plant supported by a 300 MW PV plant is being constructed on the Osborne dam, river Odzi in the Manicaland province of Zimbabwe [60]. This is the first project of its kind in the country which will provide backup for the national power grid during peak hours when the available network capacity is insufficient. Peak demand in Zimbabwe is observed for 8.5 h in a day [61,62].

Evidently from the foregoing, PHS is a mature technology that has been tried and tested. Through coordination, a higher penetration of solar PV may be achieved by using hydropower to compensate for the fluctuations in PV output in Kenya. Consequently, there will be less disruptions in electricity supply since there is reliance on both solar and hydropower.
