Solar energy in Andalusia (Spain): present state and prospects for the future

The unsustainability of the present production–consumption energy model highlights the finite nature of conventional energy resources, as well as the environmental degradation inherent in such a model. Today's environmental policies are largely devoted to fostering the development and implementation in Europe of renewable energy technologies. This paper analyses the present and future situation of renewable energy resources in Andalusia in the south of Spain, and more specifically, of solar energy with an average potential radiation of 4.6±0.3 kW h/m² per day. In Andalusia energy policies are generally implemented through regional development plans such as the Plan Energético de Andalucía (PLEAN)¹ and the Programa Andaluz de Promoción de Energías Renovables (PROSOL).² The principle objective of the latter programme is to implement and increase high-temperature solar thermal energy to 100 MW in 2006, even raising it to 230 MW in 2010. Regarding low-temperature solar thermal energy installations, there are plans to increase the quantity of m²/1000 installed per inhabitant from the present figure of 14 to a total of 142. Regarding individual installations of solar photovoltaic energy, the present aim is to cover 20.4% of the national objectives and 15% in installations connected to the electricity network. The geographic location of Andalusia in the south of Spain signifies that it is in a key position to play an important strategic role in the implementation of renewable energy technology in Europe, as well as providing sufficient energy for its own needs and even exporting such projects to other countries.     

Passive solar radiant system,SIRASOL. Physical–mathematical modeling and sensitivity analysis

When using passive solar heating systems, it is necessary to have available an Equator-facing facade on which to install them. Rooms without such a facade are not the best option for conventional passive solar heating systems. SIRASOL is a passive solar radiant system that captures solar energy and is to be installed in the ceiling of the room. This room must not necessarily have an Equator-facing facade. Solar energy heats up a metal sheet, which is the radiant panel, which transfers heat by long-wave radiation to the room below it. This paper presents a mathematical model and a sensitivity analysis. The mathematical model was used to analyze radiant panel temperature, radiant mean temperature, operative temperature and panel surface area. Results of the sensitivity study showed that when solar radiation rises (from 200 to 800 W) panel temperature increases from 36 °C to 92 °C, whereas variations in outside and inside air temperature have a negligible impact on the panel temperature. Thus, the use of SIRASOL is possible in locations with clear skies. Moreover, from panel temperature values we calculated mean radiant temperature and thereby the room’s operative temperature, which is proportional to the radiant panel area. When this area is 50% of the room’s floor area, operative temperature grows 3.1 °C higher than inside air temperature when solar radiation is 500 W/m². The analysis shows that a thermal asymmetry appears only when SIRASOL’s surface area to floor area ratio is higher than 32%.     

Spatial insolation models for photovoltaic energy in Canada

Spatial models of global insolation and photovoltaic electricity generation potential for Canada were developed. The main objective was to provide Canadians with an easily accessible, reliable tool for rapidly estimating the monthly and yearly electricity production potential of grid-connected photovoltaic systems anywhere in the country, and for assessing the dependence of production on location, time of year and array orientation. Monthly mean daily insolation data from 144 meteorological stations across Canada were used, along with data from an additional eight stations in Alaska to improve the models in that region. Several photovoltaic array orientations were considered, including South-facing arrays with latitude and vertical tilts and a sun-tracking orientation. Partial thin plate smoothing splines as implemented in ANUSPLIN were used to generate the spatial insolation models. The models were based on geographic position and a transform of monthly mean precipitation, the latter variable being a surrogate for cloudiness which affects surface insolation. Photovoltaic electricity generation (in kW h per kilowatt of photovoltaic installed power capacity) was estimated for each month and for the entire year from the insolation models by assuming international standard values for the performance ratio of photovoltaic systems. The yearly average root mean square predictive error (RTGCV) on the mean daily global insolation ranges between 0.75 (vertical tilt) and 1.43 MJ/m² (sun-tracking orientation) (or about 4.7–9.0 kW h/kW in terms of PV potential), or from 5.6% to 6.9% of the mean. Ultimately insolation and photovoltaic potential were mapped over the country at a 300 arc seconds (～10 km) resolution. The maps are available on a Natural Resources Canada Website. This is an important new tool to help Canadians gain an overall perspective of Canada’s photovoltaic potential, and allow estimation of potential photovoltaic system electricity production at any chosen location.     

Design and performance of the solar-powered floor heating system in a green building

In the green building of Shanghai Research Institute of Building Science, the evacuated tubular solar collectors with a total area of 150 m² were installed to provide heating for the covered area of 460 m². The floor heating coil pipes were made of high-quality pure copper with the dimension of Φ 12 × 0.7 mm. Under typical weather condition of Shanghai, the average heating capacity was 25.04 kW during the working hours from 9:00 to 17:00, which was sufficient to keep indoor thermal environment. The average electric COP of the floor heating system was 19.76 during the system operation. Compared with the widely used air-source heat pump heating systems with the electric COP of 3.5 in Shanghai, the solar-powered floor heating system shows great potential in energy conservation in winter. With respect to the whole heating period, the solar fraction was 56%. According to the performance analysis of the system with ambient parameters, it was observed that the system performance could be greatly enhanced with the increase of daily solar insolation. However, the system performance varied slightly with average ambient temperature. Compared with average ambient temperature, daily solar insolation had a more distinct influence on the performance of the solar-powered floor heating system.     

Performance analysis and neural modelling of a greenhouse integrated photovoltaic system

In the modern agriculture, greenhouses are well established as technological solutions aimed to increase plants productivity and crops quality. Greenhouses can include added capabilities for the energy generation by the integration of photovoltaic solar modules in their cladding areas provided that the blocking effect of photosynthetically active radiation is not significant for plants growing. After a comprehensive literature survey on the integration of photovoltaic systems in greenhouses, this work describes the results of an experience carried out at Almería (South Eastern Spain), where it has been built and monitored a 1.024 m² pilot photovoltaic greenhouse. The experimental set up has consisted of a greenhouse roof 9.79% coverage ratio by means of 24 flexible thin film modules, installed in two different checkerboard configurations. The obtained results indicate that, for the conditions of the undertaken experiment, the yearly electricity production normalised to the greenhouse ground surface is 8.25 kW h m^?2, concordant to previous findings for the used type of modules. In addition to this, an artificial neural network model has been elaborated to predict the electricity instantaneous production of the system, showing the suitability of this modelling technique for complex and non linear systems, as it is the case of the constructively integrated PV plants, either in greenhouses and buildings, where both impinging radiation and system configuration are highly constrained by the pre-existing structures.     

Design and construction of non-imaging planar concentrator for concentrator photovoltaic system

A novel configuration of solar concentrator, which is the non-imaging planar concentrator, capable of producing much more uniform sunlight and reasonably high concentration ratio, is designed and constructed. This design is envisioned to be incorporated in concentrator photovoltaic (CPV) systems. The work presented here reports on the design, optical alignment and application of the prototype, which is installed at Universiti Tunku Abdul Rahman (UTAR), Malaysia. In the architecture of the prototype, 360 flat mirrors, each with a dimension of 4.0 cm × 4.0 cm, are arranged into 24 rows and 15 columns with a total reflection area of about 5760 cm². In addition to that, illumination distribution for the prototype is simulated and its results are then compared with the experiment result.     

Hourly simulation and performance of solar electric-vapor compression refrigeration system

A solar electric-vapor compression refrigeration (SE-VCR) system has been proposed in this study. The SE-VCR system was investigated for different evaporating temperatures and months in Adana city located in the southern region of Turkey. First, the hourly cooling load capacities (heat gain) of a sample building during the 23rd days of May, June, July, August and September months were determined by using meteorological data such as hourly average solar radiations and atmospheric temperatures. The hourly total heat gain of the sample building comprised of wall, window, humans, illumination and devices were determined by using the Cooling Load Hourly Analysis Program (HAP) 4.4. Then, the hourly variations of various parameters such as coefficient of the performance, condenser capacity and compressor power consumption were calculated. In addition, the minimum photovoltaic panel surface area was determined to meet the compressor power demand according to the hourly average solar radiation data. For evaporating temperature T_e = 0 °C, the maximum compressor power consumption was obtained as 2.53 kW at 15:00 PM on August 23. The required photovoltaic panel surface area was found to be around 31.26 m². It was determined that the SE-VCR system could be used for home/office-cooling purposes during the day in the southern region of Turkey.     

Analysis of solar desiccant cooling system for an institutional building in subtropical Queensland,Australia

Institutional buildings contain different types of functional spaces which require different types of heating, ventilating and air conditioning (HVAC) systems. In addition, institutional buildings should be designed to maintain an optimal indoor comfort condition with minimal energy consumption and minimal negative environmental impact. Recently there has been a significant interest in implementing desiccant cooling technologies within institutional buildings. Solar desiccant cooling systems are reliable in performance, environmentally friendly and capable of improving indoor air quality at a lower cost. In this study, a solar desiccant cooling system for an institutional building in subtropical Queensland (Australia) is assessed using TRNSYS 16 software. This system has been designed and installed at the Rockhampton campus of Central Queensland University. The system's technical performance, economic analysis, energy savings, and avoided gas emission are quantified in reference to a conventional HVAC system under the influence of Rockhampton's typical meteorological year. The technical and economic parameters that are used to assess the system's viability are: coefficient of performance (COP), solar fraction, life cycle analysis, payback period, present worth factor and the avoided gas emission. Results showed that, the installed cooling system at Central Queensland University which consists of 10 m² of solar collectors and a 0.400 m³ of hot water storage tank, achieved a 0.7 COP and 22% of solar fraction during the cooling season. These values can be boosted to 1.2 COP and 69% respectively if 20 m² of evacuated tube collector's area and 1.5 m³ of solar hot water storage volume are installed.     

Viability of solar photovoltaics as an electricity generation source for Jordan

Viability of solar photovoltaics as an electricity generation source for Jordan was assessed utilizing a proposed 5 MW grid-connected solar photovoltaic power plant. Long-term (1994–2003) monthly average daily global solar radiation and sunshine duration data for 24 locations – distributed all over the country – were studied and analyzed to assess the distribution of radiation and sunshine duration over Jordan, and formed an input data for evaluation and analysis of the proposed plant's electricity production and economic feasibility. It was found that – depending on the geographical location – the global solar radiation on horizontal surface varied between 1.51 and 2.46 MWh/m²/year with an overall mean value of 2.01 MWh/m²/year for Jordan. The sunshine duration was found to vary – according to the location – between 8.47 and 9.68 h/day, with a mean value of 9.07 h/day and about 3311 sunshine hours annually for Jordan. The annual electricity production of the proposed plant varied depending on the location between 6.886 and 11.919 GWh/year, with a mean value of 9.46 GWh/year. The specific yield varied between 340.9 and 196.9 kWh/m², while the mean value was 270.59 kWh/m². Analysis of the annual electricity production of the plant, the specific yield, besides the economic indicators i.e., internal rate of return, simple payback period, years– to- positive cash flow, net present value, annual life cycle saving, benefit–cost ratio, and cost of energy – for all sites – showed that Tafila and Karak are the most suitable sites for the solar photovoltaic power plant's development and Wadi Yabis is the worst. The results also showed that an average of 7414.9 tons of greenhouse gases can be avoided annually utilizing the proposed plant for electricity generation at any part of Jordan.     

An assessment of solar energy potential in Kampuchea

A satellite technique was adopted to assess solar energy potential in Kampuchea. The study aims to explore solar irradiation potential and distribution under the influence of Asian monsoons over land and a large water surface of a lake by using the satellite technique, with a relatively small spatial scale, which have never been accessed before. In this study, the solar irradiation potential over Kampuchea (10°N–14.5° N, 101.5°E–105°E) was estimated at interval of half a degree grid. The seasonal variations of mean daily solar irradiation in Kampuchea were measured during two Asian winter and summer monsoon seasons.The results revealed that the mean solar irradiation depends more on orographic effects than on seasonal changes. During the winter monsoon, the local minimal means of daily solar irradiation were found on the great Lake Tonle Sap and on the northern, windward side of the Elephant Mountain with a range of 13–14 MJ m^?2 day^?1. The local maximal means of daily solar irradiation were found on the northwestern part of Kampuchea, with a value of 18 MJ m^?2 day^?1. In contrast, during the summer monsoon, the local minimal means of daily solar irradiation were, again, found on the same mountainous region of the Elephant Mountain, but the area of minimal means shifted to the southern side where it is the windward side of the mountain during the summer monsoon with a value of 12 MJ m^?2 day^?1. The local maximal means of the daily solar irradiation were found scattered over various areas: south of Lake Tonle Sap and at various places in the north and northwestern parts of the country, with a range of 18–19 MJ m^?2 day^?1. It was also found that a high mean of solar irradiation is generally associated with a low standard deviation, i.e., it is less in temporal variation.     

Feasibility of pico-hydro and photovoltaic hybrid power systems for remote villages in Cameroon

Pico-hydro (pH) and photovoltaic (PV) hybrid systems incorporating a biogas generator have been simulated for remote villages in Cameroon using a load of 73 kWh/day and 8.3 kWp. Renewable energy systems were simulated using HOMER, the load profile of a hostel in Cameroon, the solar insolation of Garoua and the flow of river Mungo. For a 40% increase in the cost of imported power system components, the cost of energy was found to be either 0.352 €/kWh for a 5 kW pico-hydro generator with 72 kWh storage or 0.396 €/kWh for a 3 kWp photovoltaic generator with 36 kWh storage. These energy costs were obtained with a biomass resource cost of 25 €/tonne. The pH and PV hybrid systems both required the parallel operation of a 3.3 kW battery inverter with a 10 kW biogas generator. The pH/biogas/battery systems simulated for villages located in the south of Cameroon with a flow rate of at least 92 l/s produced lower energy costs than PV/biogas/battery systems simulated for villages in the north of Cameroon with an insolation level of at least 5.55 kWh/m²/day. For a single-wire grid extension cost of 5000 €/km, operation and maintenance costs of 125 €/yr/km and a grid power price of 0.1 €/kWh, the breakeven grid extension distances were found to be 12.9 km for pH/biogas/battery systems and 15.2 km for PV/biogas/battery systems respectively. Investments in biogas based renewable energy systems could thus be considered in the National Energy Action Plan of Cameroon for the supply of energy to key sectors involved in poverty alleviation.     

Application of Sayigh “Universal Formula” for global solar radiation estimation in the Niger Delta region of Nigeria

In recent years, renewable energy utilisation in various applications has increased significantly. Applications involving solar thermal energy include air and water heating whilst solar photovoltaic systems have been installed to provide electricity for households in urban and rural areas of the developing economies. The solar radiation data are not easily available for many countries and is therefore estimated most of the times. In this work is presented the results of evaluating the Sayighr “Universal formula” for estimating the global solar radiation in the Niger Delta region of Nigeria with Umudike (longitude 7.33°E, latitude 5.29°N) as a case study. The levels of the global solar radiation which ranged from 1.99 kWh to 6.75 kWh, computed with the method are in agreement with those of earlier authors indicating that the method can be used for reproducing signatures of global solar radiation in the region when actual measurements are not available.     

Projections of future changes in solar radiation in China based on CMIP5 climate models

Surface solar radiation research is important for understanding future climate change and the application of large-scale photovoltaic systems. We used the coupled model intercomparison project phase 5 (CMIP5) under the RCP8.5 scenario to project potential changes in surface solar radiation, surface temperatures, and cloud fractions between 2006 and 2049 in China, as well as how these changes may affect photovoltaic power generation. The results show that the following. (1) For surface temperatures, the median trends of all considered models show warming in China of 0.05 K/year. The maximum positive trends for all-sky radiation appear in the southeast of China, reaching 0.4 W/m²/year. Cloud cover exhibits a mainly decreasing trend in the overall region of China. (2) The all-sky radiation of most selected regions shows a decreasing trend. The maximum negative value (− 0.08 W/m²/year) appears in Qinghai. (3) Compared with the average photovoltaic power output from 2006 to 2015, the photovoltaic power output in western China will decrease by − 0.04 %/ year, while photovoltaic power output in southeastern China will increase by 0.06–0.1%/year.     

Maximising the energy output of a PVT air system

Simultaneously generating both electricity and low grade heat, photovoltaic thermal (PVT) systems maximise the solar energy extracted per unit of collector area and have the added benefit of increasing the photovoltaic (PV) electrical output by reducing the PV operating temperature. A graphical representation of the temperature rise and rate of heat output as a function of the number of transfer units NTUs illustrates the influence of fundamental parameter values on the thermal performance of the PVT collector. With the aim of maximising the electrical and thermal energy outputs, a whole of system approach was used to design an experimental, unglazed, single pass, open loop PVT air system in Sydney. The PVT collector is oriented towards the north with a tilt angle of 34°, and used six 110 Wp frameless PV modules. A unique result was achieved whereby the additional electrical PV output was in excess of the fan energy requirement for air mass flow rates in the range of 0.03–0.05 kg/s m². This was made possible through energy efficient hydraulic design using large ducts to minimise the pressure loss and selection of a fan that produces high air mass flow rates (0.02–0.1 kg/s m²) at a low input power (4–85 W). The experimental PVT air system demonstrated increasing thermal and electrical PV efficiencies with increasing air mass flow rate, with thermal efficiencies in the range of 28–55% and electrical PV efficiencies between 10.6% and 12.2% at midday.     

Performance comparison of a double-axis sun tracking versus fixed PV system

In the present study, performance results of two double axis sun tracking photovoltaic (PV) systems are analyzed after one year of operation. Two identical 7.9 kWp PV systems with the same modules and inverters were installed at Mugla University campus in October 2009. Measured data of the PV systems are compared with the simulated data. The performance measurements of the PV systems were carried out first when the PV systems were in a fixed position and then the PV systems were controlled while tracking the sun in two axis (on azimuth and solar altitude angles) and the necessary measurements were performed. Annual PV electricity yield is calculated as 11.53 MW h with 1459 kW h/kWp energy rating for 28 fixed tilt angle for each system. It is calculated that 30.79% more PV electricity is obtained in the double axis sun-tracking system when compared to the latitude tilt fixed system. The annual PV electricity fed to grid is 15.07 MW h with 1908 kW h/kWp for the double axis sun-tracking PV system between April-2010 and March-2011. The difference between the simulated and measured energy values are less than 5%. The results also allow the comparison of different solutions and the calculation of the electricity output.     

Performance simulation of solar-boosted ocean thermal energy conversion plant

Ocean thermal energy conversion (OTEC) is a power generation method that utilizes small temperature difference between the warm surface water and cold deep water of the ocean. This paper describes the performance simulation results of an OTEC plant that utilizes not only ocean thermal energy but also solar thermal energy as a heat source. This power generation system was termed SOTEC (solar-boosted ocean thermal energy conversion). In SOTEC, the temperature of warm sea water was boosted by using a typical low-cost solar thermal collector. In order to estimate the potential thermal efficiency and required effective area of a solar collector for a 100-kWe SOTEC plant, first-order modeling and simulation were carried out under the ambient conditions at Kumejima Island in southern part of Japan. The results show that the proposed SOTEC plant can potentially enhance the annual mean net thermal efficiency up to a value that is approximately 1.5 times higher than that of the conventional OTEC plant if a single-glazed flat-plate solar collector of 5000-m² effective area is installed to boost the temperature of warm sea water by 20 K.     

MODERGIS application: Integrated simulation platform to promote and develop renewable sustainable energy plans,Colombian case study

This research presents the MODERGIS Integrated Simulation's Platform as a tool to promote and develop renewable energy plans under sustainability criteria, in order to increment the participation of renewable technologies in the national “energy mix” and shows an application to Colombia as a case study. Potential zones of solar and wind energy and productive areas were determined for bio-energies, by means of a geographical information system which simulated energy scenarios influenced by climatic phenomena up to the year 2030. Results yield potentials of 26,600 MW in wind energy and 350,000 MW in solar energy. Bioenergy potentiates in a sustainable way of 366,310 km per biomass, 291,486 km in African palm, 9,667 km in sugar cane. These scenarios were simulated in a supply/demand with time horizons up until 2030, including an analysis of the effects on the energy systems of the El Niño Southern Oscillation atmospheric component (ENSO). Finally, in order to obtain an appropriate mix of renewable sources that could be introduced in the national energy mix, the Multi-Criteria Analysis method VIKOR was used, allowing to perform performing 5151 possible combinations of renewable projects; the optimal selection corresponds to 600 MW from wind power, 740 MW solar photovoltaic and 660 MW solar thermoelectric. Giving these results to the new scene allowed for incrementing the participation of renewable technologies up to a 0.23% in the current year and up to a 7% of the “energy mix” in the year 2030.     

The wind power of Mexico

The high price of fossil fuels and the environmental damage they cause have encouraged the development of renewable energy resources, especially wind power. This work discusses the potential of wind power in Mexico, using data collected every 10 min between 2000 and 2008 at 133 automatic weather stations around the country. The wind speed, the number of hours of wind useful for generating electricity and the potential electrical power that could be generated were estimated for each year via the modelling of a wind turbine employing a logistic curve. A linear correlation of 90.3% was seen between the mean annual wind speed and the mean annual number of hours of useful wind. Maps were constructed of the country showing mean annual wind speeds, useful hours of wind, and the electrical power that could be generated. The results show that Mexico has great wind power potential with practically the entire country enjoying more than 1700 h of useful wind per year and the potential to generate over 2000 kW of electrical power per year per wind turbine installed (except for the Chiapas's State). Indeed, with the exception of six states, over 5000 kW per year could be generated by each turbine.     

Analysis of off-grid hybrid wind turbine/solar PV water pumping systems

While many remote water pumping systems exist (e.g. mechanical windmills, solar photovoltaic, wind-electric, diesel powered), few combine both the wind and solar energy resources to possibly improve the reliability and the performance of the system. In this paper, off-grid wind turbine (WT) and solar photovoltaic (PV) array water pumping systems were analyzed individually and combined as a hybrid system. The objectives were to determine: (1) advantages or disadvantages of using a hybrid system over using a WT or a solar PV array alone; (2) if the WT or solar PV array interfered with the output of the other; and (3) which hybrid system was the most efficient for the location. The WT used in the analysis was rated at 900 W alternating current (AC). There were three different solar PV arrays analyzed, and they were rated at 320, 480, and 640 W direct current (DC). A rectifier converted the 3-phase variable voltage AC output from the WT to DC before combining it with the solar PV array DC output. The combined renewable energies powered a single helical pump. The independent variable used in the hybrid WT/PV array analysis was in units of W/m². The peak pump efficiency of the hybrid systems at Bushland, TX occurred for the 900 W WT combined with the 640 W PV array. The peak pump efficiencies at a 75 m pumping depth of the hybrid systems were: 47% (WT/320 W PV array), 51% (WT/480 W PV array), and 55% (WT/640 W PV array). Interference occurred between the WT and the different PV arrays (likely due to voltage mismatch between WT and PV array), but the least interference occurred for the WT/320 W PV array. This hybrid system pumped 28% more water during the greatest water demand month than the WT and PV systems would have pumped individually. An additional controller with a buck/boost converter is discussed at end of paper for improvement of the hybrid WT/PV array water pumping system.     

Development of the high concentration III-V photovoltaic system at INER,Taiwan

The 100 kW high concentration photovoltaic (HCPV) system has been constructed in October 2007 at the Institute of Nuclear Energy Research (INER), Taiwan. The maximum module efficiency with a geometrical concentration ratio of 476× is about 26.1% under 850 W/m² DNI and passive cooling conditions [Cherng-Tsong Kuo. The project of demonstrating MW high concentration photovoltaic (HCPV) system. Science and technology yearbook of Taiwan. ROC; 2008]. The 100 kW HCPV system consists of 14 sets of pillar-stand 5 kW systems and 21 sets of roof-top 1.5 kW systems. Each 5 kW system and 1.5 kW are comprised of 40 modules and 12 modules respectively. Each module was integrated with 40 solar cells with 35% conversion efficiency each, manufactured by Spectrolab Company, the highest III-V solar cell conversion efficiency record keeper. This project is the pioneer for the establishment of one MW HCPV demonstration system in 2008.