Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: further improvements by ortho-image analysis and application to Turin (Italy)

The ongoing rush of the UE member states to the 2020 overall targets on the national renewable energy share (see Directive 2009/28/EC), is propelling the large exploitation of the solar resource for the electricity production. However, the incentives to the large employment of PV solar modules and the relative perspective profits, are often cause of massive ground-mounted installations. These kind of installations are obviously the preferred solution by the investors for their high economic yields, but their social impact should be also considered. Over the Piedmont Region for instance, the large proliferation of PV farms is jeopardizing wide agricultural terrains and turistic areas, therefore the policy of the actual administration is to encourage the use of integrated systems in place of massive installations. For these reasons, an effort to demonstrate that the distributed residential generation can play a primary role in the market is mandatory. In our previous work “Scalable methodology for the photovoltaic solar energy potential assessment based on available roof surface area: application to Piedmont Region (Italy)”, we already proposed a basic methodology for the evaluation of the roof-top PV system potential. However, despite the total roof surface has been computed on a given cartographical dataset, the real roof surface available for PV installations has been evaluated through the assumption of representative roofing typologies and empirical coefficients found via visual inspection of satellite images. In order to overcome this arbitrariness and refine our methodology, in the present paper we present a brand new algorithm to compute the available roof surface, based on the systematical analysis and processing of aerial georeferenced images (ortho-images). The algorithm, fully developed in MATLAB®, accounts for shadow, roof surface available (bright and not), roof features (i.e. chimneys or walls) and azimuthal angle of the eventual installation. Here we apply the algorithm to the whole city of Turin, and process more than 60,000 buildings. The results achieved are finally compared with our previous work and the updated PV potential assessment is consequently discussed

Deep-sea reverse osmosis desalination for energy efficient low salinity enhanced oil recovery

The decrease in the oil discoveries fuels the development of innovative and more efficient extraction processes. It has been demonstrated that Enhanced Oil Recovery (EOR, or tertiary recovery technique) offers prospects for producing 30 to 60% of the oil originally trapped in the reservoir. Interestingly, oil extraction is significantly enhanced by the injection of low salinity water into oilfields, which is known as one of the EOR techniques. Surface Reverse Osmosis (SRO) plants have been adopted to provide the large and continuous amount of low salinity water for this EOR technique, especially in offshore sites. In this article, we outline an original solution for producing low salinity water for offshore EOR processes, and we demonstrate its energy convenience. In fact, the installation of reverse osmosis plants under the sea level (Deep-Sea Reverse Osmosis, DSRO) is found to have significant potential energy savings (up to 50%) with respect to traditional SRO ones. This convenience mainly arises from the non-ideality of reverse osmosis membranes and hydraulic machines, and it is especially evident - from both energy and technological point of view - when the permeate is kept pressurized at the outlet of the reverse osmosis elements. In perspective, DSRO may be a good alternative to improve the sustainability of low salinity EOR

Techno-economic analysis of a solar thermal plant for large-scale water pasteurization

Water pasteurization has the potential to overcome some of the drawbacks of more conventional disinfection techniques such as chlorination, ozonation and ultraviolet radiation treatment. However, the high throughput of community water systems requires energy-intensive processes, and renewable energy sources have the potential to improve the sustainability of water pasteurization plants. In case of water pasteurization by solar thermal treatment, the continuity of operation is limited by the intermittent availability of the solar irradiance. Here we show that this problem can be addressed by a proper design of the plant layout, which includes a thermal energy storage system and an auxiliary gas boiler. Based on a target pasteurization protocol validated by experiments, a complete lumped-component model of the plant is developed and used to determine the operating parameters and size of the components for a given delivery flow rate. Finally, we report an economic analysis of the proposed plant layout, which allows its optimization for different scenarios based on two design variables, namely the solar multiple and the duration of the thermal energy storage. Based on the analyzed cases, it is found that the proposed plant layouts may yield a unit cost of water treatment ranging from ≈32 EUR-cents m−3 to ≈25 EUR-cents m−3

Techno-economic analysis of a solar thermal plant for large-scale water pasteurization

Water pasteurization has the potential to overcome some of the drawbacks of more conventional disinfection techniques such as chlorination, ozonation and ultraviolet radiation treatment. However, the high throughput of community water systems requires energy-intensive processes, and renewable energy sources have the potential to improve the sustainability of water pasteurization plants. In case of water pasteurization by solar thermal treatment, the continuity of operation is limited by the intermittent availability of the solar irradiance. Here we show that this problem can be addressed by a proper design of the plant layout, which includes a thermal energy storage system and an auxiliary gas boiler. Based on a target pasteurization protocol validated by experiments, a complete lumped-component model of the plant is developed and used to determine the operating parameters and size of the components for a given delivery flow rate. Finally, we report an economic analysis of the proposed plant layout, which allows its optimization for different scenarios based on two design variables, namely the solar multiple and the duration of the thermal energy storage. Based on the analyzed cases, it is found that the proposed plant layouts may yield a unit cost of water treatment ranging from ≈32 EUR-cents m-3 to ≈25 EUR-cents m-3

Data-driven appraisal of renewable energy potentials for sustainable freshwater production in Africa

Clean water scarcity plagues several hundred million people worldwide, representing a major global problem. Nearly half of the total population lacking access to safe and drinkable water lives in Africa. Nonetheless, the African continent has a remarkable yet untapped potential in terms of renewable energy production, which may serve to produce clean water from contaminated or salty resources and for water extraction and distribution. In this view, the analysis of possible scenarios relies on data-driven approaches due to the scale of the problem and the general lack of comprehensive, direct on-site experience. In this work, we aim to systematically review and map the renewable potentials against the freshwater shortage in Africa to gain insight on perspective possible policies and provide a readily usable and well-structured framework and database for further analyses. All reported datasets are critically discussed, organized in tables, and classified by a few metadata to facilitate their usability in further analyses. The accompanying discussion focuses on regions that, in the near future, are expected to significantly exploit their renewable energy potentials, and on the reasons at the basis of the local water shortage, including technological and distribution problems

Deep-sea reverse osmosis desalination for energy efficient low salinity enhanced oil recovery

The decrease in the oil discoveries fuels the development of innovative and more efficient extraction processes. It has been demonstrated that Enhanced Oil Recovery (EOR, or tertiary recovery technique) offers prospects for producing 30 to 60% of the oil originally trapped in the reservoir. Interestingly, oil extraction is significantly enhanced by the injection of low salinity water into oilfields, which is known as one of the EOR techniques. Surface Reverse Osmosis (SRO) plants have been adopted to provide the large and continuous amount of low salinity water for this EOR technique, especially in offshore sites. In this article, we outline an original solution for producing low salinity water for offshore EOR processes, and we demonstrate its energy convenience. In fact, the installation of reverse osmosis plants under the sea level (Deep-Sea Reverse Osmosis, DSRO) is found to have significant potential energy savings (up to 50%) with respect to traditional SRO ones. This convenience mainly arises from the non-ideality of reverse osmosis membranes and hydraulic machines, and it is especially evident – from both energy and technological point of view – when the permeate is kept pressurized at the outlet of the reverse osmosis elements. In perspective, DSRO may be a good alternative to improve the sustainability of low salinity EOR

Sustainable freshwater production using passive membrane distillation and waste heat recovery from portable generator sets

More than two billion people live in areas affected by water stress. In some coastal regions, freshwater supply has been progressively improved by large-scale desalination systems, which are nowadays mostly driven by non-renewable energy sources. Here we discuss, and experimentally investigate, the use of small-scale desalination devices for freshwater production powered by waste heat from electric power generators. The water purification technology relies on a passive, multi-stage and thermally-driven membrane distillation device, recently proposed by some of the authors of this work. The distiller is powered by low-grade (temperature lower than 80 °C) waste heat, recovered from the coolant circuit of small diesel engines for electricity production. Field experiments show that, for the tested engine, up to 1.12 kW m-2 can be recovered in standard operating conditions, which yield a nearly 2.61 L m-2 h-1 freshwater production from seawater. A lumped parameter model, validated by experiments, shows that this productivity could be eventually enhanced by tuning the number of distillation stages. Utilization with exhaust gases, and thus higher feeding working temperatures, is also discussed. The proposed solution may provide a sustainable, simple, inexpensive and efficient means for freshwater production from recovered waste heat, which would otherwise be wasted to the ambient. Therefore it could be particularly effective, for instance, for field hospitals in remote or impoverished areas, especially in emergency situations