Technical University of Hamburg, Germany
Abstract: In spite of the significant need for energy and the large power of solar radiation (insolation) available in Turkmenistan the use of solar energy is still in a starting phase. In this paper a strategy is lined out how this deficit may be overcome, starting from a large number of affordable small and medium-sized photovoltaic solar plants. Details for various types of multi-purpose and dedicated solar plants are explained. Investment costs may be significantly lowered by the assembly of solar panels and the production of connectors, wiring and special accumulators within Turkmenistan. PV solar panels produce a much loweramount of greenhouse gases than Diesel generators resulting in a significant contribution to climate change mitigation.
Keywords: solar energy, photovoltaic, insolation, multipurpose solar plants, dedicated solar plants, production within Uzbekistan, greenhouse gases, climate change mitigation
In most places in Central Asia there is ample sunshine (http://solargis.com/products/maps-and-gis-data/free/overview/) that calls for an application in the generation of heat by solar heating and electrical power using the photovoltaic (PV) effect. PV solar elements are mass-produced using bulk monocrystalline, polycrystalline and amorphous silicon, also several thin-film combinations of semiconducting alloys are used in practice. Typical conversion efficiencies nowadays are in the range of 15 to 25 %.
When talking about large scale solar energy application two approaches can be chosen:
Top-down: Very large solar stations are constructed with one or severalmegawatt output power for a centralized electricity supply requiring a multi-million USDinvestment that in Central Asia generally only can be implemented on a government-level or in government-dominated energy-supply corporations. Centralized energy production requires a reliable supply grid that may not be available in many areas.
Bottom-up: A large quantity of smaller solar stations (5 to 50 kWpeak) can be constructed by private business and distributed right at the locations of the end consumer. Using internet control these stations may be monitored as well asinterconnected to larger local electricity grids (decentralized power grids). The investment per station naturally is much lower and in general can be afforded by the end consumer who receives an added value in his work. In other cases small credit schemes will be useful to spur investments.
Configurations of solar stations
Photovoltaic power stations or shortly –PV solar stations – are classified according to table 1:
Station #1 and #2 feed the energy produced by the solar panels (yield) into the public grid, type 2 also additionally allows that part of the yield is diverted for customer use. The stand-alone station # 3 and # 4 operate independent of the public grid.
When calculating the cost of solar energy in relation to Diesel generators and the public grid two important cases I and II have to be distinguished and to be compared with the energy from the grid (III and IV):
- 100% efficiency: The energy produced by PV solar stations or Diesel generators is totally exploited, i.e. the total energy produced (stand-by energy) is equal to the energy used by the customer. This is true for the following types of PV solar stations according to table 1:
# 1: The total electrical energy produced is fed into the grid,
# 2: Part of the electrical energy is used by the client, the rest is fed into the grid,
#5:The total electrical energy produced is used for operating water pump(s) or equivalent equipment.
Table 1: Types of solar stations
- Efficiency less or only temporarily equal to 100%: This is the case when the stand-by energy is larger or only temporarily equal to the energy consumed. In practice this corresponds to the situation when the customer according to his needs applies variable loads to the generating system (PV solar,Diesel generator, or grid) any time of the day. Diesel generators have a stand-by energy that is relatedto the maximum power needed by the customer. When the load is smaller at various times of the customer work cycle a part of the stand-by energy is lost, leading to an efficiency that can be significantly lower than 100%. This case is typical for Diesel generators and naturally leads to high average prices per kWh consumed.
The stand-alone PV solar systems # 3 and # 4 in table 1 have the advantage of energy storage by batteries (accumulators): At day time they can deliver electric energy whenever the customer demands it, otherwise the energy produced is used for charging the batteries, from which energy can be extracted any time according to the work cycle of the customer. Energy can only be lost when at sunlight the batteries are already fully charged which can be avoided. This is why the cost of the energy extracted from stand-alone PV solar stations generally is lower than the energy produced by Diesel generators, often quite significantly.
- Energy from the grid: In most Central Asian countries the electricity price from the grid is heavily subsidized by the government to an amount as low as 0.03 USD per kWh. This price tag cannot be equaled by Diesel generators or solar stations. On the other hand, due to the in many areas overaged public grid technology – stemming even from Soviet times – electricity supply often cannot be provided in a reliable way – leading to regular black-outs up to several hours a day – especially in small villages and rural areas. This can lead to severe losses in work productivity of the end user that in many cases cancompensatefor the higher costs of PV solar energy.
- A different calculation has to be taken into account when the consumer site is located far away from an access to the public grid: From local sources a price tag of € 8.382 was given for a 1 km extension of a public grid power line, that may be written off in about 20 years. For a 5 km additional power line (that can be quite realistic) even the cost of the public grid is not lower than that of PV solar stations of the type # 3 and # 4, and even much higher compared to the type # 5. If the present subsidized extreme low price of 0.03 Euro will not be maintained in the coming years (this is discussed already presently) the calculation will change even more in favor of solar systems.
Solar energy applications specific for Central Asia
In Turkmenistan and generally in Central Asia specific applications further support the exploitation of PV solar stations:
- In rural areas presently a large demand is expressed for water pumping in fertile (often virgin) land distant from farming villages: In mountainous areas the ground water is unsalted and may be used directly, while in the plains (typical for steppes) the ground water is often salty and cannot be exploited directly. In that casesweet water from rivers may be used exploitingthe existing network of irrigation pipelines and canals. Calculations from farming experts show that the use of dedicated PV solar pumping stations can be highly profitable when valuable crops are grownthat requirea limited demand for irrigation like wine, nuts, or pomegranates, and others. Of course, drip irrigation should be used as a standard in order to minimize water and energy consumption.
- The mass application of PV solar-driven pumps (or equivalent equipment, see table 1) of the #5 type is favored by the strongly reduced investment cost of dedicated PV solar stations: Solar stations of this type do not need inverters and batteries and hence are much less expensive than the other types of solar stations. Taking also into account that they do not require maintenance they are clearly superior to Diesel generators – especially in distant locations. In view of the large added value to agricultural production this application most likely will lead to the most strongly developing applications of PV solar energy in Turkmenistan and other Central Asian countries.
- Another important aspect is that much of the agricultural land presently used in Central Asia is contaminated already from Soviet times by salinization, caused by excessive irrigation, as well as of the remains of an intensive use of fertilizers, pesticides, and fungicides – all leading to reduced crops and an decreasing acceptance by the localconsumers of the products. Fertile new land (virgin land) – when irrigated with the support of dedicated PV solar-driven water pumps – therefore is an attractive option for the near future.
- The foregoing option opens the way even to agricultural technologies of bioproductionthat are still underdeveloped in Central Asia: Taking into account the favorite climate of Central Asia for the production of high quality fruits and vegetables PV solar-irrigated virgin land can solve the imminent problem that in many cases neither fresh nor dried fruits and vegetables may be exported to Western countries due to the residual contents of fertilizers, pesticides, and fungicides exceeding the limits defined by legislation. In Central Asia this could create new attractiveoptionsto increase the export market for ecologically clean grown or even biologically certified food products.
- The demand for solar stations of the #3 and # 4 type depends largely on the special situation at the place of the future customers: In areas with a fragilepower supply by the public grid including total black-outsPV solar stations in many cases are obviously profitable. This concerns both high-productivity farming as well as small and medium-size enterprises that cannot work profitably without a reliable permanent power supply.
It can be generally stated that practically all Diesel engines so far installed and planned for the future can be replaced profitably by PV solar stationsof the types # 3 and # 4. The limited life time of Diesel engines and the permanent need for maintenance and control generally favors this development.
There is a multitude of further applications, ranging from the power supply of remote relais stations for communication, especially in view of the quite developed mobile phone system in countries like Turkmenistan, to public health institutions, police stations, as well as for all kinds of emergency facilities, and many other applications.
A very important aspect is the enormous impact of the large scaleexploitation of PV solar energy in the climate change mitigation,as demonstratedby the fact that – taking into account all possible contributions starting from the production of the system to the operation up to the end of the anticipated life time of the equipment– the emission of greenhouse gases is 17 times lower for PV solar stations in the range of 7 kWpin comparison to equivalent Diesel generators (fig. 1 and 2):
Fig. 1: Factors contributing to the greenhouse gas emission of a PV solar station (M. Kaltschmitt and A. Rödl, to be published).
Cost reduction for PV solar equipment
An often-heard argument against the introduction of PV solar equipment is the high investment cost for the acquisition of the PV solar system. PV stations require expensive high technology components that partly presently cannot be produced in a competitive way within the Central Asian countries.On the other hand it is evident that, in principle, the investment costs can be cutnearly into half when a proportion ofPV solar station components are produced within Turkmenistan by private business (mostly small and medium-sized enterprises), like:
- Assembly of solar panels
- Production of dedicated accumulators for PV stations using low-cost conventional lead technologies andpossiblyyearly maintenance cycles including repair and recycling. In this area practical experience still has to be acquired by the Uzbek companies – preferably in cooperation with European battery producers.
- Connectors and wiring
- Pavilions (housing) for PV solar stations
Of course, specific knowledge acquisition is necessary in every of these components.
Finally, financial support by foreign and/orTurkmen credit lines could significantly speed up the implementation of a large-scale introduction of solar energy in Turkmenistan.
It has been demonstrated that in Central Asia the conditions foralarge-scale exploitation of PV solar energy are quite favorable: Small and medium-sized PV solar stations of are technically and economically feasible and prove to be significantly more cost-effective that the previously used Diesel generators. Necessary measures for a fast grow of the solar-energy application include a extensive training and know-how transfer, consulting and the start of “learning by doing” within Turkmenistan and the surrounding Central Asian countries.
PV solar technologies can spur the development of agricultural production in the direction of ecologically cleaner products, as well as the productivity of smaller and medium-sized companies – especially in areas with a limited public power supply.
The production of an increasing share of PV solar technology components in the country will create high-tech working places as well as reduce investment costs for Turkmen solar energy users.
Finally – and maybe as one of the the most important arguments – the large-scale use of PV solar energy will give a significant contribution to the conservation of the surrounding environment and for an effective climate change mitigation – that is most urgent in regions like Central Asia. /// nCa
About the author: Prof. Dr. Hanno Schaumburg is professor emeritus at the Hamburg University of Technology. He can be reached at firstname.lastname@example.org