Bekir Turgut1, Rok Stropnik2 Thermal Energy Storage for Efficient Utilisation of Solar Energy presentation of situation in Slovenia and Turkey Halime Paksoy1, Uros Strith2, Hunay Evliya1, Vincenc Butala2, Bekir Turgut1, Rok Stropnik2 Çukurova University Adana, Turkey University of Ljubljana, Slovenia

INTRODUCTION Solar energy is so abundant that one hour of sun shine on earth covers world energy demand for an entire year. Therefore, solar energy needs to be stored for efficient utilization Thermal energy storage is realized as a result of the change in internal energy of any material.

INTRODUCTION TES concepts involve utilization of one or a combination of the following heats: Sensible heat Latent heat Chemical reaction heat Duration of the storage can be: short or diurnal (day/night) long or seasonal (summer/winter)

INTRODUCTION For seasonal storage (summer/winter), underground thermal energy storage (UTES) is the only option currently used in solar plants. This paper attempts to give an overview of solar energy potential and the recent storage technologies used in solar applications in Turkey and Slovenia.

Current energy situation in Turkey Figure 1: Breakdown of consumption of energy sources according to sector in Turkey Recently Turkey has 70 million of population with 1.8% growth rate. Annual income is approximately 9.000 USD/capita in 2010, which is 3 times as much in 2000.

Current energy situation in Turkey Figure 2: Electricity generation by fuel sources of Turkey Ministry’s official estimated target is to reach an energy-saving potential of 30% in the residential consumption, 20% in the industry, and 15% in the transportation.

Solar energy potential in Turkey Figure 3: Solar radiation of Turkey

Solar energy potential in Turkey Table 1: Monthly Average Solar Potential of Turkey  Solar energy potential is calculated as 380 billion kWh/year (See Table)

Laws and legislations on renewable energy in Turkey Turkey has recently enacted its first renewable energy law in 2005 (Law No. 5346). The aim of this law’s is to encourage the use of renewable energy resources (wind, solar, geothermal, biomass etc.) EU commission’s target is to increase this share to 20% till 2020. Solar energy potential is calculated as 380 billion kWh/year.Table gives monthly solar energy rate and sunshine duration.

Solar energy for domestic hot water production in Turkey Table 2: Contribution of solar collectors to the primary energy production in Turkey Turkey is one of the leading countries in the world with a total installed capacity of 8,2 million m² collector area as of the systems are mostly used in Aegean and Mediterranean regions. Total energy production equals to 290 000 TOE

SLOVENIA General about energy in Slovenia Energy use in Slovenia is increasing in the recent 15 years and is based on solid fuels, nuclear energy and renewable sources of energy. Consumption of primary energy was 305,7 PJ in 2007. In the last ten years energy consumption increased to 32 PJ, which represents 11.7 % growth.

SLOVENIA General about energy in Slovenia Figure1: Energy in Slovenia (year 2007): left primary energy, right final energy

SLOVENIA General about energy in Slovenia Final energy in Slovenia is divided into three major groups: traffic, industry and households. Final energy in Slovenia (PJ) households Final energy in Slovenia (PJ) industry

SLOVENIA Renewable sources of energy Renewable sources of energy (RES) are important source of primary energy in Slovenia, increasing of their share is one of the priorities of energy and environmental policies of the state. Share of RES (including large hydroelectric power stations) in energy balance of Slovenia in the year 2000 represents 9,2 % of all primary energy. With 9,2 % share of renewable sources (biomass 3,9 %) in primary energy balance, Slovenia was on fifth place in EU (average in European Union was 5.5 %).

SLOVENIA Renewable sources of energy Figure 3: Share [PJ] of renewable sources of energy in Slovenia (2007)

SLOVENIA Solar energy and its storage In Slovenia we have installed 100.000 m2 of solar energy collectors or 0.05 m2 per inhabitant, if some data has been considered as a base (Switzerland 0,02 m2, Austria 0.09 m2) Only short-term thermal energy storage is now being used in households in Slovenia Measurements of environmental data have been realized in Slovenia for many years. Among others measurements, solar radiation is one of the most predominant.

SLOVENIA Solar energy and its storage Figure 4: Potential of solar energy in Slovenia

SLOVENIA Solar energy and its storage Table 1: Data for average day solar radiation in Slovenia From the results we can conclude that solar radiation is non-uniform in year cycle. The use of solar energy is therefore closely connected to energy storage.

SLOVENIA Solar energy and its storage Theoretical potential of solar radiation in Slovenia can be calculated related to the area of the State is 93700 PJ/a The potential must be reduced because we must exclude forests, fields, rivers and roads. Therefore the total potential of solar radiation is 19200 PJ/a Technical potential of solar radiation with consideration of all roofs in houses is 300 PJ/a

SLOVENIA Researches, grants and action plan Solarge Solair The project Res-e regions Ministry of Economy prepared the first draft of the National Action Plan for renewable energy sources for the period 2010-2020

SLOVENIA Researches, grants and action plan This year EKO FUND released a call of grants for non- repayable financial stimulations for new investment of use of renewable sources of energy and larger energy efficiencies of residential buildings Figure 5: Number of subsidized systems in Slovenia

CONCLUSIONS AND RECOMMENDATIONS For efficient utilization of solar energy, compact and cost-effective storage systems with high energy storage density are essential; There is an urgent need to exploit the solar energy to meet the growing energy demand and to sustain the life on earth; Once solar systems are mass produced like conventional, fossil energy systems, and integrated into buildings, thus replacing conventional systems they will become competitive; A corrective pricing mechanism, such as a carbon tax, will also help competitiveness.