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.     

Development modes analysis of renewable energy power generation in North Africa

North African countries generally have strategic demands for energy transformation and sustainable development. Renewable energy development is important to achieve this goal. Considering three typical types of renewable energies— wind, photovoltaic (PV), and concentrating solar power (CSP)—an optimal planning model is established to minimize construction costs and power curtailment losses. The levelized cost of electricity is used as an index for assessing economic feasibility. In this study, wind and PV, wind / PV / CSP, and transnational interconnection modes are designed for Morocco, Egypt, and Tunisia. The installed capacities of renewable energy power generation are planned through the time sequence production simulation method for each country. The results show that renewable energy combined with power generation, including the CSP mode, can improve reliability of the power supply and reduce the power curtailment rate. The transnational interconnection mode can help realize mutual benefits of renewable energy power, while the apportionment of electricity prices and trading mechanisms are very important and are related to economic feasibility; thus, this mode is important for the future development of renewable energy in North Africa.     

Assessment of renewable energy resources potential for electricity generation in Bangladesh

Renewable energy encompasses a broad range of energy resources. Bangladesh is known to have a good potential for renewable energy, but so far no systematic study has been done to quantify this potential for power generation. This paper estimates the potential of renewable energy resources for power generation in Bangladesh from the viewpoint of different promising available technologies. Estimation of the potential of solar energy in Bangladesh is done using a GIS-based GeoSpatial Toolkit (GsT), Hybrid System Optimization Model for Electric Renewables (HOMER) model and NASA Surface Meteorology and Solar Energy (SSE) solar radiation data. The potential of wind energy is estimated by developing a Bangladesh wind map using NASA SSE wind data and HOMER model. A review of country's biomass and hydro potential for electricity generation is presented. The technical potential of gird-connected solar PV is estimated at 50,174 MW. Assuming that 1000 h per year of full power is the feasible threshold for the exploitation of wind energy, the areas that satisfy this condition in the country would be sufficient for the installation of 4614 MW of wind power. The potential of biomass-based and small hydro power plants is estimated at 566 and 125 MW, respectively. The renewable energy resources cannot serve as alternative to conventional energy resources, yet they may serve to supplement the long-term energy needs of Bangladesh to a significant level.     

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.     

Ebeam fabrication of silicon nanodome photovoltaic devices without metal catalyst contamination

In this paper, the fabrication of silicon nanodome solar cells on crystalline wafers is reported. Crystalline silicon was patterned by ebeam lithography to define the silicon nano pillars with diameter of 100 nm, 1 μm and 5 μm. Unlike conventional bottom up growth of silicon nanowire from gold (Au), our method is free from contaminant. Consequently, it is a valuable method to fully evaluate the effect of nanostructures on solar cell performances. The fabricated devices were characterized through scanning electron microscopy, absorption measurements, illuminated solar cell I–V characteristics and monochromatic incident photon-to-electron conversion efficiency.     

The Hokuto mega-solar project

Solar generation systems are one of the measures for reducing global warming. An installed capacity target of solar generation systems in our country will be set 4.82 GW in 2010, while the total installed capacity is still 1.92 GW in 2007. About 80% of the systems are mainly residential use and each is very small. Constructions of some large-scale solar generation systems will be expected and intensive development of related technologies are urgent. The New Energy and Industrial Technology Development Organization (NEDO) advertised for consignment research business “Verification of Grid Stabilization with Large-scale Photovoltaic (PV) Power Generation Systems” in 2006. The verification tests are carried out in two sites of Hokuto City, Yamanashi Prefecture and Wakkanai City, Hokkaido. The outlines and the developing targets and some of studying results of the Hokuto mega-solar project (HMSP) are introduced in this paper.     

Environmental,technical and financial feasibility study of solar power plants by RETScreen,according to the targeting of energy subsidies in Iran

In this study, based on new electricity tariffs, three scenarios have been developed with The RETScreen International Photovoltaic Project Model, according to the targeting of energy subsidies in Iran. We have also dedicated one of our scenarios to the reduction of greenhouse gasses.In the first case the electricity price was set to 3.75 Cents/kWh (450 Rial/kWh) and no credit was assigned to the reduction of greenhouse gasses (GHG), therefore equity payback (Return positive cash flow) has been 12.1 year. In the second case the electricity price was set to 17.5 Cents/kWh, therefore equity payback (return positive cash flow) was 8 year. Finally in the last scenario by considering a credit to the reduction of greenhouse gasses and electricity price being 175 Cents/kWh and applying solar panels with high efficiency and suitable batteries (DOD = 60%), equity payback (return positive cash flow) reached within 6 years.     

Solar greenhouse assisted biogas plant in hilly region – A field study

The present study was undertaken with the objective of evaluating plastic as an alternative material for biogas plant on a par with conventional brick material. The field study was carried out for one year (October, 2005–September, 2006) in a small hamlet at Nilgiris incorporating solar energy to study its influence on biogas production. During summer (April–June) the temperature reaches to the maximum of 21–25 °C and the minimum of 10–12 °C. During winter (October–December), the temperature available is maximum of 16–21 °C and minimum of 2 °C. The solar insolation in the study area ranges from 250 to 600 W/m². This study involves the control conventional Deenabandhu model (Indian standard model prevailing in most part of India made of masonry structure only) and the experimental plastic tank with greenhouse canopy of similar capacity. Our previous work [Vinoth Kumar, K., Kasturi Bai, R., 2005. Plastic biodigesters – a systematic study. Energy for Sustainable Development 9 (4), 40–49] on lab scale digester made from plastic material was compared over other materials and the results gave us much confidence to carry out further study on pilot scale. In continuation, a semi-continuous study was conducted for one year with the retention time of 55 days. The gas generated from the biogas plants was utilized for cooking (burner) and lighting (lamp) purposes. The yearly average slurry temperatures recorded during the study period was 26.3 and 22.4 °C in experimental and control biogas plants against ambient temperature of 17.0 °C. The yearly average greenhouse chamber temperature recorded was 29.1 °C in the experimental biogas plant. The yearly average gas yield from the experimental and control biogas plants were 39.1 and 34.6 l kg^?1 day^?1 respectively. Gas productions in the winter season registered lower than other months. It can be concluded that the solar greenhouse assisted plastic biogas plant can be efficiently adopted with minor modifications in hilly regions since the temperature profile plays a major role in biogas production.     

Wave climate off the Swedish west coast

This paper presents and discusses the wave climate off the Swedish west coast. It is based on 8 years (1997–2004) of wave data from 13 sites, nearshore and offshore, in the Skagerrak and Kattegat. The data is a product of the WAM and SWAN wave models calibrated at one site by a wave measurement buoy. It is found that the average energy flux is approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the nearshore Skagerrak, and 2.4 kW/m in the Kattegat. One of the studied sites, i.e. site 9, is the location of a wave energy research site run by the Centre for Renewable Electric Energy Conversion at Uppsala University. This site has had a wave power plant installed since the spring of 2006, and another seven are planned to be installed during 2008. Wave energy as a renewable energy source was the driving interest that led to this study and the results are briefly discussed from this perspective.     

Improvement of multicrystalline silicon solar cell performance via chemical vapor etching method-based porous silicon nanostructures

In this paper, we report on the effect of chemical vapor etching-based porous silicon (PS) on the performance of multicrystalline silicon solar cells performed via deep n⁺/p junction-type structures. Chemical vapor etching of silicon leads to the formation of porous silicon (PS) nanostructures that dramatically decrease the surface reflectivity from 30% to about 8%, and increase the minority carrier diffusion lengths from 90 μm to 170 μm. As a result, the short-circuit current density was improved by more than 20% and the fill factor (FF) by about a 10%. An enhancement of the photovoltaic conversion energy efficiency of the solar cells from 7% to 10% was observed. This low-cost PS formation process can be applied in the photovoltaic cell technology as a standard procedure.     

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.     

Can distributed generation offer substantial benefits in a Northeastern American context? A case study of small-scale renewable technologies using a life cycle methodology

Renewable distributed electricity generation can play a significant role in meeting today's energy policy goals, such as reducing greenhouse gas emissions, improving energy security, while adding supply to meet increasing energy demand. However, the exact potential benefits are still a matter of debate. The objective of this study is to evaluate the life cycle implications (environmental, economic and energy) of distributed generation (DG) technologies. A complementary objective is to compare the life cycle implications of DG technologies with the centralized electricity production representing the Northeastern American context. Environmental and energy implications are modeled according to the recommendations in the ISO 14040 standard and this, using different indicators: Human Health; Ecosystem Quality; Climate Change; Resources and Non-Renewable Energy Payback Ratio. Distinctly, economic implications are modeled using conventional life cycle costing. DG technologies include two types of grid-connected photovoltaic panels (3 kWp mono-crystalline and poly-crystalline) and three types of micro-wind turbines (1, 10 and 30 kW) modeled for average, below average and above average climatic conditions in the province of Quebec (Canada). A sensitivity analysis was also performed using different scenarios of centralized energy systems based on average and marginal (short- and long-term) technology approaches. Results show the following. First, climatic conditions (i.e., geographic location) have a significant effect on the results for the environmental, economic and energy indicators. More specifically, it was shown that the 30 kW micro-wind turbine is the best technology for above average conditions, while 3 kWp poly-crystalline photovoltaic panels are preferable for below average conditions. Second, the assessed DG technologies do not show benefits in comparison to the centralized Quebec grid mix (average technology approach). On the other hand, the 30 kW micro-wind turbine shows a potential benefit as long as the Northeastern American electricity market is considered (i.e., oil and coal centralized technologies are affected for the short- and long-term marginal scenarios, respectively). Photovoltaic panels could also become more competitive if the acquisition cost decreased. In conclusion, DG utilization will represent an improvement over centralized electricity production in a Northeastern American context, with respect to the environmental, energy and economic indicators assessed, and under the appropriate conditions discussed (i.e., geographical locations and affected centralized electricity production scenarios).     

Monolithically series-interconnected transparent modules of dye-sensitized solar cells

We have realized a new type of dye-sensitized solar cell (DSC) modules. The monolithically series interconnected structure, which is similar to the structure of amorphous silicon solar cells (SCs), was employed so that the advantages of DSCs compared to conventional silicon SCs (low costs, low energy consumption in production processes) were fully exploited. To achieve other important features of DSCs (transparency and color choice) we have developed transparent counter electrodes (CEs) composed of Pt-loaded In₂O₃:Sn nanoparticles and separators composed of SiO₂ nanoparticles to replace conventional non-transparent ones used in the modules. The performance of the new CEs is significantly improved to be close to those of conventional ones during electric generation operations. In all 85% of the maximal conversion efficiency was maintained after 2000 h of a durability test under 1 sun light soaking at 60 °C.     

Residential building envelope heat gain and cooling energy requirements

We present the energy use situation in Hong Kong from 1979 to 2001. The primary energy requirement (PER) nearly tripled during the 23-year period, rising from 195,405 TJ to 572,684 TJ. Most of the PER was used for electricity generation, and the electricity use in residential buildings rose from 7556 TJ (2099 GWh) to 32,799 TJ (9111 GWh), an increase of 334%. Air-conditioning accounted for about 40% of the total residential sector electricity consumption. A total of 144 buildings completed in the month of June during 1992–2001 were surveyed. Energy performance of the building envelopes was investigated in terms of the overall thermal transfer value (OTTV). To develop the appropriated parameters used in OTTV calculation, long-term measured weather data such as ambient temperature (1960–2001), horizontal global solar radiation (1992–2001) and global solar radiation on vertical surfaces (1996–2001) were examined. The OTTV found varied from 27 to 44 W/m² with a mean value of 37.7  W/m². Building energy simulation technique using DOE-2.1E was employed to determine the cooling requirements and hence electricity use for building envelope designs with different OTTVs. It was found that cooling loads and electricity use could be expressed in terms of a simple two-parameter linear regression equation involving OTTV.     

Situation and outlook of solar energy utilization in Tibet,China

The near-exponential rise in tourist numbers and accelerating economic growth have challenged Tibetan energy supply and threaten its peculiar environment and valuable ecosystem. Exploitation of pollution free solar power may medicate this demand for energy. Here we shall provide a review of solar power development in Tibet. This region has a near inexhaustible source of solar energy due to its average annual radiation intensity of 6000–8000 MJ/m², ranking it first in China and second after the Sahara worldwide. Currently, Tibet has 400 photovoltaic power stations with a total capacity of nearly 9 MW. In addition, 260,000 solar energy stoves, passive solar house heating covering 3 million square meters, and 400,000 m² of passive solar water heaters are currently in use in Tibet. Although Tibet places first in applying solar energy in China, solar energy faces big challenges from hydroelectric power and the absence of local know-how. The new power generation capacity in Tibet's “11th Five-Year (2006–2010)” Plan focuses primarily on hydropower, PV power stations being relegated to a secondary role as supplementary to hydropower. Here it will be argued that this emphasis is incorrect and that solar energy should take first place in Tibet's energy development, as it is crucial in striving for a balance between economic development, booming tourism, and environmental protection.     

Current status of ground source heat pumps in Korea

In Korea, ground source heat pumps (GSHP) have been gaining popularity for space heating and cooling. Because there are few sources of high-temperature geothermal energy in the country, public baths (25–40 °C) and geothermal heat pumps (～15 °C) using low-temperature groundwater or ground are the most dominant direct geothermal uses. The Promotion Law of the New and Renewable Energy Development, Use and Dissemination, enacted in 2004, imposed an obligatory installation of space heating and cooling systems using new and renewable energy sources including geothermal energy for newly constructed public buildings (more than 5% of total construction cost). Between 2004 and 2007, ground source heat pump systems occupied about 60% of the total public installation of new and renewable energy equipment. Starting with 35.2 kW of two facilities in 2000, systems with the capacity of over 127.1 MWt have been installed in 551 buildings (facilities) as of August 2008. The vertical closed heat pump system (closed loop) and the groundwater heat pump system (standing column well type; SCW) occupied 65.1% and 29.3%, respectively, among the total GSHP systems installed. The depth of the vertical loops ranged between 65 and 250 m (average 159 m) and the well depth of the SCW system ranged between 150 and 600 m (average 391 m). The number of geothermal energy companies, installing the GSHP systems, that are officially registered in the relevant authority increased from 5 in 2000 to 397 in July 2008. This paper presents details of the current status of ground source heat pumps in Korea.     

Solid-phase crystallization of amorphous silicon on ZnO:Al for thin-film solar cells

The suitability of ZnO:Al thin films for polycrystalline silicon (poly-Si) thin-film solar cell fabrication was investigated. The electrical and optical properties of 700 -nm-thick ZnO:Al films on glass were analyzed after typical annealing steps occurring during poly-Si film preparation. If the ZnO:Al layer is covered by a 30 nm thin silicon film, the initial sheet resistance of ZnO:Al drops from 4.2 to 2.2 Ω after 22 h annealing at 600 °C and only slightly increases for a 200 s heat treatment at 900 °C. A thin-film solar cell concept consisting of poly-Si films on ZnO:Al coated glass is introduced. First solar cell results will be presented using absorber layers either prepared by solid-phase crystallization (SPC) or by direct deposition at 600 °C.     

Contribution of renewable energy sources to electricity production in the autonomous community of Navarre (Spain): A review

Economic development in recent decades has been characterised by the increased use of fossil fuels. Clearly, a significant amount of this energy does not fall in line with the principles of sustainable development, either because of its contaminating effect or because of its non-renewable nature.Today, Navarre generates around 60% of its electricity requirements by means of wind power and small hydropower stations. On the downside, Navarre's energy consumption is above average for the European Union and its economy is growing at an annual rate in excess of 5%. The Castejón (800 MW) thermal power stations, scheduled for enlargement, generate more energy than Navarre's entire wind power sector.In terms of hydroelectric power, there are around 200 small hydropower plants in operation. In addition, the Autonomous Community of Navarre has installed a biomass plant in Sangüesa, with an installed output of 25 MW, annually generating 200 GWh through the combustion of 160,000 t of cereal straw.In addition, Navarre, specifically Tudela, is the site of the largest solar energy plant in Spain, producing 1.2 MWp, following its connection to the grid at the beginning of the year. Two thirds of the 10,080 panels are arranged in a central body and the remaining third are panels pertaining to different technologists and technologies involved in research and development.