SOLAR POWER: CONCENTRATED SOLAR POWER AND PHOTOVOLTAIC PLANTS COMPARISON AND THEIR APPLICABILITY IN TAJIKISTAN

by Gulnoza Khodizoda

Abstract

This paper’s main focus is to give an overview of the current potential of solar energy utilization through the use of solar power plants and the applicability of this to lower income countries, with a case study on Tajikistan. We will discuss two main types of solar power plants: Concentrated Solar Power (CSP) and Photovoltaic (PV), and will argue that at the current stage, PV plants are more feasible and preferred for Tajikistan. The case of Tajikistan helps to conclude that in lower income countries, PV plants appear to be a more preferred technology to be deployed, but is limited to small-scale PV systems only.

Key words: solar energy, solar power plant, PV, CSP, lower income countries, Tajikistan, Central Asia

Introduction

Solar energy is the irradiation received from the sun and is considered to be the cleanest and most abundant renewable energy source available.[1] Solar energy is converted from thermal to electrical energy to create solar power, which is then used to meet energy demand. To meet their energy demands and diversify energy sources, solar energy is being actively used by industrialized countries. Germany is the world leader in solar energy use, with 41 GW installed as of 2016. The success of the country can mostly be explained by favorable conditions for the business, with skilled companies and good financing opportunities as well as strong public awareness about solar energy technologies. With the increased global interest in solar energy use, developing countries now also see the opportunity to deploy solar power in order to decrease their dependency on more expensive energy sources, and ensure energy security.

This paper aims to investigate the potential of building a solar power plant in a lower income country as to provide off-grid electricity for rural and remote areas and to contribute to the countries’ energy security. The essay is organized as follows: it starts with an overview of solar power plants (SPP), differentiating between two types: Concentrated Solar Power (CSP) and Photovoltaic (PV). After this, it analyses the case of Tajikistan, first reviewing the country’s current energy system and continuing with the potential of building a SPP. The paper concludes with a discussion on the general applicability of SPP in lower income countries.

Concentrated Solar Power

Solar power plants convert sunlight into electricity, either directly or indirectly. Two main types of solar power plants can be distinguished: Concentrated Solar Power (CSP) and Photovoltaic (PV) power plants. Concentrated Solar Power (CSP), also called a solar thermal power plant, uses sunlight to heat a transfer fluid.[3] To produce electricity, heat is then used to operate the conventional power cycle and to drive a generator.[4] CSP has a storage system and might be hybridized with fossil fuels to meet the energy needs during low and non-solar periods. One of the examples of CSP technology is the solar power tower given in Figure 1.[5]

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Figure 1. Schematics of a CPS Plant. Source: Pavlovic et al, 2012, A Review of Concentrating Solar Power Plants in the World and Their Potential Use in Serbia.

A solar power tower consists of a field of heliostats, which focuses solar irradiation onto the solar receiver. Then a transfer fluid, which can be water, molten salt, liquid sodium or air, is heated. Mechanical work is then converted to electrical energy by a steam generator after which it is sent to the distributive grid. The cycle is repeated by steam from the turbine being condensed and sent to the boiler to be heated by the solar receiver again.

One of the main benefits of the CSP plant is that, for more stable operating, it can be hybridized with other fossil fuels.[6] The other benefits of CSP include low operation costs, high efficiency and the possibility to utilize thermal storage to better match supply with demand.

The barrier for utilizing CSP technology is the need for relatively high investments.[7] That is, the construction and installation costs are high, and it is more expensive due to the new technology involved. A CSP plant requires a considerable amount of space and it is highly location dependent, as the intensity of solar energy, availability of water and presence of infrastructure play a significant role in site selection. To avoid significant transmission losses, CSP should be constructed close to the electrical grid.

Photovoltaic

Photovoltaic (PV) power plants convert solar radiation directly into electricity.[8] Figure 2 shows an example of a solar PV plant.[9] At the first stage, solar PV modules are used to collect solar radiation. The output received from the PV modules is called DC electricity. Then the DC electricity passes to inverters where it is converted to alternating current (AC) electricity to be transmitted to the utility grid through an AC Service Panel.

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Figure 2. Overview of a Solar PV Power Plant. Source: Pavlovic et al, 2012.

PV, like the other methods of solar power generation, is a clean energy that does not emit greenhouse gasses. PV power generation is silent, as it does not use any other fuel but sun rays. Moreover, it can be constructed nearly everywhere, as it generates electricity directly from sunlight and requires minimal maintenance. PV is a fast growing industry, with rapidly improving technology and expertise available, which makes it more cost competitive compared to other solar power generators. PV can be constructed in any size to meet energy needs and be enlarged when needed.

However, there are some barriers in adopting PV. As PV uses direct sunlight, it is not efficient during nights or under clouds. It also cannot meet heating demands due to being available foremost during hot seasons. PV does not have storage capacity and requires grid connection for a stable use. PV systems have a relatively low efficiency of around seventeen to forty percent.[10]

There are a number of differences between CSP and PV plants. One of the advantages of PV plant is that it takes only six to twelve months[11] to build and can be installed everywhere where CSP can, but not vice versa.[12] PV is a technology that could cover power plant and residential sectors, whereas CSP is only commercially feasible in large scale projects. PV plants can be used in a decentralized power system, while the transmission grid is essential for CSP. One of the other characteristics of PV is that it can use not only direct sunlight but also diffuse radiation and, as such, can be installed at any location. CSP, in turn, needs direct solar irradiation, and the areas where it can be built are quite limited. This makes PV technology relatively simple to implement. As a result, developers and companies have focused on improving PV technology to decrease the costs associated with PV cells and PV power plants. However, there is no possibility of electricity storage in PV systems as there is in CSP plants. Nevertheless, PV is the technology that is widely spread across the world with an estimated 292 GW of installed capacity at of the end of 2016, whereas CSP capacity constitutes less than 5 GW.[13] Therefore, with all its benefits, a PV plant appears to be the more preferred technology to be deployed at the first stages of utilizing solar energy.

Energy System of Tajikistan

Tajikistan is one of the poorest countries in the Central Asian region with the majority of the population – around seventy three percent – living in rural areas with seasonal power shortages.[14] Out of these, around ten percent live in remote mountainous areas with poor or no access to an adequate electricity supply.[15]

The problem is mainly due to the bad condition of the transmission and distribution systems, which also results in inefficiency and significant electricity losses. The rural population is most affected by the situation and there are no real electricity grid renovation programs in those areas.

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Graph 1. Urban Share of Energy Consumption in Tajikistan

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Graph 2. Rural Share of Energy Consumption in Tajikistan

Source: World Bank, Central Asia Longitudinal Inclusive Society Survey (CALISS), 2013

Potential to use CSP in Tajikistan

Tajikistan has an excellent environment and climate to utilize its solar energy potential.[17] The country is located on 36°40’ and 41°05’ of the northern latitude and 67°31’ and 75°14’ of the eastern longitude.[18] It has 280 to 330 sunny days, with estimated 2100 to 3000 hours of solar energy, per year.[19] The solar radiation intensity varies in the highlands from 360 to 1120 MJ/m2 and from 280 to 925 MJ/m2 in the foothills. With a solar potential of around 25 billion kWh/year, Tajikistan could satisfy an estimated ten to twenty percent of its total energy demand with solar power. However, the current use of solar energy is limited to solar greenhouses, improved solar stoves, and solar water heaters.

Graph 1 shows the energy consumption of the urban population and graph 2 shows the rural share. It is clear that the urban population has better electricity and natural gas supplies, whereas the rural population mainly relies on wood, coal and other biomass energy resources. The most severe situation occurs during the five months of winter when rural households receive less than four hours of electricity a day. As such, in order to heat a single room, an average household uses four tons of coal, making it a big financial burden for the family.[16] The usage of renewable energy sources could improve the situation of those households and solve problems with energy shortages.

The feasibility to build CSP has its own specific features. Apart from essential meteorological requirements, one should also consider other key criteria, some of which are discussed below.[20]

Direct Normal Irradiance (DNI).[21]

DNI is a measurement of the amount of solar radiation received by a unit area that is perpendicular to the incoming sunrays. To provide a viable energy yield for CSP, the DNI should be at least 2000 kWh/m2 per year.[22] Figure 3 shows the DNI map for Tajikistan. It is clearly seen from the map that the highest DNI is concentrated in eastern part of Tajikistan. Despite the availability of DNI, its concentration in mountainous areas makes building CSP in those sites highly unlikely, due to both a lack of flat land available and remoteness. However, to meet the local needs, other construction sites can be considered.

 

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Figure 3. Direct Noram Irradiation (DNI), Tajikistan. Source: Solargis, 2016.

                          Local Water Resources[23]

In CSP, water is primarily used as a cooling agent for steam turbine condensers. Tajikistan has abundant water resources, but the sites with the highest DNI often have limited water availability and the choice of a construction site should consider an optimal amount of both DNI and water resources available.

Grid Connection[24]

The electrical grid is essential for a CSP plant, and the distance between the plant and the grid should be minimal to avoid additional costs. Unfortunately, grid connection is the biggest obstacle for Tajikistan as rural areas have poor or no access to it. Moreover, the construction of new electrical grids would significantly increase the cost of the plant.

Proximity of Roads[25]

Roads are important during the construction phase of the plant and are furthermore needed during the operation stage. This constraint is more crucial for a CSP plant than for small scale PV because of the relative flexibility in site selection of a PV plant. However, there is no infrastructure in the mountainous areas of Tajikistan, which is especially problematic when we consider that those are the areas with the highest DNI concentration

At the stage of the project development, a comprehensive feasibility analysis should be carried out with a focus on the specific requirements of CSP. The assessment of some of the key criteria helps to conclude that CSP construction for Tajikistan is a long and challenging process.

Potential to use PV in Tajikistan

The International Finance Corporation has released a set of guidelines for stakeholders interested in running PV projects titled: ‘Utility-Scale Solar Photovoltaic Power Plants’.[26] This publication provides comprehensive information on each step in realizing a PV project from project development and agreements to construction, operation, maintenance, and financing the project. For the purpose of this study and in order to understand the potential of building PV plants in Tajikistan, our analysis has been made using Section 6 of the criteria of the IFC guidelines; ‘Site Selection’.

Although there are no clear rules for the site selection, there are some main constraints that are essential in the assessment. These include solar resources, available land, local climate, topography, environmental designations, geotechnical conditions, geopolitical risks, accessibility, grid connection, module soiling, water availability, financial incentives, land use and local regulations.[27] The most impactful of these constraints is discussed below.

Solar Resources[28]

Tajikistan is located in the so-called ‘Sun Belt’, which refers to the sunniest countries with higher solar radiation. The country has on average 2500-3000 hours of sunshine in a year. As such, it is estimated that, if the solar energy potential would be fully utilized, sixty to eighty percent of the energy demand of the rural population could be met for ten months of the year and using biomass for the remaining two months.[29] However, when we consider the mountainous areas, shading can arise as a potential problem, due to the fact that even a small area of shade can significantly impact the energy output.

Grid Connection[30]

As previously stated, grid connection is the key constraint for Tajikistan, due to the poor condition of the electrical grid, which has unstable voltage and frequent power cut-offs. Conversely, PV plants can be constructed off-grid. Moreover, an estimated ten percent of the population lives in off-grid, remote, mountainous areas.[31] As such, the feasibility of constructing a new grid, as well as the possibility of renewing the old electricity grid, is low and it would significantly increase the cost of a PV project.

Water Availability[32]

Water availability need not be a constraint in Tajikistan. Although less urgent than with CSP, water availability is also a positive factor for a PV plant during project development and sites with better water access should be given preference. Apart from that, PV plants have an advantage to run on diffused solar energy.

Financial Incentives.[33]

Currently, Tajikistan does not have a favorable investment climate and few incentives exist. However, there is an opportunity for the government to create those incentives, as building solar plants would bring more long-term benefits to the country in terms of better living conditions, energy efficiency and energy security.

When we look at the above-mentioned constraints, we see that although there are challenges to developing PV in Tajikistan, the conditions are generally more favorable than in the case of CSP. PV is preferable to CSP because it is more flexible in terms of needed investments, plant size and location as well as PV’s ability to use both direct and diffused solar radiation.

Additionally, the fact that building a solar power plant requires much expertise as well as detailed feasibility assessments to overcome the constraints discussed above, solar projects might become even more difficult to implement when we consider the current socioeconomic conditions in Tajikistan. The potential barriers are found in financial, legislative, institutional, educational and technological spheres as well as in the energy market itself.[35] Financial barriers include the poverty of the population, the limited availability of public and private funds, inappropriate tariff policies and an unfavorable investment climate. Legislative barriers include the absence of a legislative framework as well as inefficient regulations and strategies for the renewable energy sector. Institutional barriers consist of non-transparent management and ownership mechanisms in the energy sector, as well as corruption and weak governance. Educational and technological barriers are connected to the insufficient governmental support of Research and Development (R&D) activities, a lack of qualified staff and inadequate infrastructure. The energy market itself is very inflexible, with a low rate of reform, an underdeveloped framework of the new technologies market and no real incentives for private sector participation.

The analysis of the possibility to construct solar power plants in Tajikistan showed that PV solar is a more feasible option than CSP. However, after a more detailed discussion of the constraints in building PV plants, and looking at the socioeconomic barriers, we have to put the feasibility and probability of any future construction of the solar power plant in question.

The only way would be to construct small-scale PV systems, which require fewer investments, and can be built off-grid to meet the needs of a particular territory. Small-scale PV systems represent an autonomous system which supplies electricity directly to the household, and can be used for electricity and lightning.

One thing is certain: Tajikistan is in need of renewable energy usage, and especially of solar energy in remote areas of the country, where the possibility to use other resources is very limited. However, the roll-out of PV solar would only be possible with active government support and strong political will, where the aim should be increased governance, transparency and accountability as well as the creation of a strong legal base and incentive programs to attract donors and investments.

Conclusions

The possibility to utilize solar energy provides an opportunity to lower income countries in terms of improving living standards of the population as well as ensuring better energy security. The analysis of CSP and PV solar power plants has shown that CSP is heavily location specific as it has unique requirements to be considered in site selection, which greatly limits the choice of CSP construction sites. Countries with high DNI, water availability, infrastructure and good investment climate might utilize CSP technology, but considering the high costs involved this is not the case for lower income countries. On the other side, PV plants, with their competitive cost, flexible plant size and usage of both direct and diffused solar radiation, are more feasible to be constructed in lower income countries.

The case of Tajikistan helps to conclude that in lower income countries, a PV plant appears to be the more preferred technology to be deployed at the first stages of utilizing solar energy. However, as countries lack a large-scale electricity grid and have other socioeconomic barriers, the construction potential of solar power plants becomes very limited and is only possible for small-scale PV systems.

Gulnoza Khodizoda is currently working in Alif Capital, a Tajikistan-based microfinance organization. Gulnoza holds a MA degree in Economic Governance and Development from OSCE Academy in Bishkek, Kyrgyzstan.

[1] UNDP, 2000. World Energy Assessment, 2000. [pdf] Available at: http://www.undp.org/content/dam/aplaws/publication/en/publications/environment-energy/www-ee-library/sustainable-energy/world-energy-assessment-energy-and-the-challenge-of-sustainability/World%20Energy%20Assessment-2000.pdf [Accessed 1 July 2016].

[2] Fraunhofer ISE, 2017. Recent Facts about Photovoltaics in Germany. Available at: https://www.ise.fraunhofer.de/content/dam/ise/en/documents/publications/studies/recent-facts-about-photovoltaics-in-germany.pdf [Accessed 5 May 2017].

[3] Pavlovic, T., Radonijic, I, Milosavljevic, D & Pantic L., 2012. A Review of Concentrating Solar Power Plants in the World and Their Potential Use in Serbia. Renewable and Sustainable Energy Reviews, 16(6), pp. 3891 – 3902. [pdf] Available at: http://sci-hub.cc/10.1016/j.rser.2012.03.042

[4] Pavlovic, T., 2012. A Review of Concentrating Solar Power Plants in the World and Their Potential Use in Serbia.

[5] Idem.

[6] Idem.

[7] Idem.

[8] International Finance Corporation, 2015. Utility-Scale Solar Photovoltaic Power Plants: A Project Developer’s Guide. Available at: https://www.ifc.org/wps/wcm/connect/f05d3e00498e0841bb6fbbe54d141794/IFC+Solar+Report_Web+_08+05.pdf?MOD=AJPERES [Accessed 29 June 2016].

[9] International Finance Corporation, 2015. Utility-Scale Solar Photovoltaic Power Plants: A Project Developer’s Guide.

[10] Karakaya, E., and Sriwannawit P., 2015. Barriers to the Adoption of the Photovoltaic Systems: The State of Art. Renewable and Sustainable Energy Reviews, 49, pp. 60-66. [pdf] Available at: http://www.sciencedirect.com.sci-hub.cc/science/article/pii/S1364032115003287

[11] International Finance Corporation, 2015.

[12] Mohaghegh, S., 2015. CSP vs PV – Understanding the Current Situation and Future Outlook. Available at: https://blogs.ucl.ac.uk/sustainable-resources/2015/11/30/csp-vs-pv-understanding-the-current-situation-and-future-outlook/ [Accessed 1 July 2016].

[13] IRENA , 2017. Renewable Capacity Statistics 2017. [pdf] Available at: http://www.irena.org/DocumentDownloads/Publications/IRENA_RE_Capacity_Statistics_2017.pdf

[14] Energy Charter Secretariat, 2013. In-Depth Energy Efficiency Review: Tajikistan. [pdf] Available at: http://www.energycharter.org/fileadmin/DocumentsMedia/IDEER/IDEER-Tajikistan_2013_en.pdf

[15] Energy Charter Secretariat, 2013. In-Depth Energy Efficiency Review: Tajikistan.

[16] Idem.

[17] Idem.

[18] Idem.

[19] Idem.

[20] Stoddard, L., Owens, B., Morse, F. & Kearney, D., 2005. New Mexico Concentrating Solar Plant Feasibility Study. [pdf] Available at: http://www.emnrd.state.nm.us/ECMD/RenewableEnergy/documents/NMCSP-draft-final-rpt-02-05.pdf

[21] Stoddard, L. et. al., 2005. New Mexico Concentrating Solar Plant Feasibility Study.

[22] Lovegrove, K. & Stein, W., 2012. Concentrating Solar Power Technology: Principles, Developments and Applications, Cambridge: Woodhead Publishing. Available at: http://www.sciencedirect.com/science/book/9781845697693

[23] Stoddard, L. et al, 2005.

[24] Idem.

[25] Idem.

[26] International Finance Corporation, 2015.

[27] Idem.

[28] Idem.

[29] UNECE, 2013. Research study for the Republic of Tajikistan within the framework of the project “The use of clean, renewable and / or alternative energy technologies for rural areas in Central Asia. [pdf] Available at: http://www.unece.org/fileadmin/DAM/project-monitoring/5-sustainable-energy/E234/2014_NationalStudies/TJ/TJ_Report.pdf

[30] International Finance Corporation, 2015.

[31] Energy Charter Secretariat, 2013.

[32] International Finance Corporation, 2015.

[33] Idem.

[34] Kayumov, A., Kabutov, K., 2014. Socio-Economic Assessment of the Production and Consumption of Renewable Energy Sources in the Republic of Tajikistan. [pdf] Available at: http://waterwiki.net/images/6/63/Renewable_Energy_assessment_Tajikistan_(Eng).pdf [Accessed 10 June 2016].

[35] Kayumov, A., Kabutov, K., 2014. Socio-Economic Assessment of the Production and Consumption of Renewable Energy Sources in the Republic of Tajikistan.

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