Entries by Carl Berntsen

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Ground Irradiance Modelling: Of Key Importance for Designing Nature Inclusive Solar Parks and Agrivoltaics Systems

Solar electricity from solar parks in rural areas are cost effective and can be deployed fast therefore play an important role in the energy transition. The optimal design of a solar park is largely affected by income scheme, electricity transport capacity, and land lease costs. Important design parameters for utility-scale solar parks that may affect landscape, biodiversity, and soil quality are ground coverage ratio, size, and tilt of the PV tables. Particularly, low tilt PV at high coverage reduces the amount of sunlight on the ground strongly and leads to deterioration of the soil quality over the typical 25-year lifetime. In contrast, vertical PV or an agri-PV design fairly high above the ground leads to more and homogeneous ground irradiance; these designs are favored for pastures and croplands. In general, the amount and distribution of ground irradiance and precipitation will strongly affect which crops can grow below and between the PV tables and whether this supports the associated food chain. As agrivoltaics is the direct competition between photosynthesis and photovoltaics. Understanding when, where and how much light reaches the ground is key to relate the agri-PV solar park design to the expected agricultural and electricity yields.

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Agrivoltaic Systems Design and Assessment: A Critical Review, and a Descriptive Model Towards a Sustainable Landscape Vision (Three-Dimensional Agrivoltaic Patterns)

As an answer to the increasing demand for photovoltaics as a key element in the energy transition strategy of many countries—which entails land use issues, as well as concerns regarding landscape transformation, biodiversity, ecosystems and human well-being—new approaches and market segments have emerged that consider integrated perspectives. Among these, agrivoltaics is emerging as very promising for allowing benefits in the food–energy (and water) nexus. Demonstrative projects are developing worldwide, and experience with varied design solutions suitable for the scale up to commercial scale is being gathered based primarily on efficiency considerations; nevertheless, it is unquestionable that with the increase in the size, from the demonstration to the commercial scale, attention has to be paid to ecological impacts associated to specific design choices, and namely to those related to landscape transformation issues. This study reviews and analyzes the technological and spatial design options that have become available to date implementing a rigorous, comprehensive analysis based on the most updated knowledge in the field, and proposes a thorough methodology based on design and performance parameters that enable us to define the main attributes of the system from a trans-disciplinary perspective. The energy and engineering design optimization, the development of new technologies and the correct selection of plant species adapted to the PV system are the areas where the current research is actively focusing in APV systems. Along with the continuous research progress, the success of several international experiences through pilot projects which implement new design solutions and use different PV technologies has triggered APV, and it has been met with great acceptance from the industry and interest from governments. It is in fact a significant potential contribution to meet climate challenges touching on food, energy, agriculture and rural policies. Moreover, it is understood—i.e., by energy developers—as a possible driver for the implementation of large-scale PV installations and building integrated agriculture, which without the APV function, would not be successful in the authorization process due to land use concerns. A sharp increase is expected in terms of number of installations and capacity in the near future. Along this trend, new concerns regarding landscape and urban transformation issues are emerging as the implementation of APV might be mainly focused on the efficiency of the PV system (more profitable than agriculture), with insufficient attention on the correct synergy between energy and food production. The study of ecosystem service trade-offs in the spatial planning and design for energy transition, to identify potential synergies and minimize trade-offs between renewable energy and other ecosystem services, has been already acknowledged as a key issue for avoiding conflicts between global and local perspectives. The development of new innovative systems (PV system technology) and components (photovoltaic devices technology) can enhance the energy performance of selected design options for APV greenhouse typology.

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Comprehensive Solar Thermal Integration for Industrial Processes

This report shows industrial processes for comprehensive solar integration. The paper discusses solar thermal energy-integration methods, cost estimations of system components and solar fractions. Multiple case study examples relevant to the dairy and biothermal industry are presented. Each case study includes three scenarios, and the results of each of those are discussed here.

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Development of a Solar-Powered Submersible Pump
System Without the Use of Batteries in Agriculture

The purpose of this study was to describe the development of a solar-powered submersible pump system without the use of batteries in agriculture. The submersible pump system used a solar drive to run it. The implementation uses a combination of solar trackers, water storage tanks, power converters, and stabilizers. The results of the study explained that solar trackers increased the efficiency of solar units that track the sun throughout the day and convert solar energy into DC electrical power.

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Wavelength-Selective Solar Photovoltaic Systems: Powering Greenhouses for Plant Growth at the Food-Energy-Water Nexus

Wavelength-Selective Photovoltaic Systems (WSPVs) combine luminescent solar cell technology with conventional silicon-based PV, thereby increasing efficiency and lowering the cost of electricity generation. WSPVs absorb some of the blue and green wavelengths of the solar spectrum but transmit the remaining wavelengths that can be utilized by photosynthesis for plants growing below. WSPVs are ideal for integrating electricity generation with glasshouse production, but it is not clear how they may affect plant development and physiological processes. The effects of tomato photosynthesis under WSPVs showed a small decrease in water use, whereas there were minimal effects on the number and fresh weight of fruit for a number of commercial species. Although more research is required on the impacts of WSPVs, they are a promising technology for greater integration of distributed electricity generation with food production operations, for reducing water loss in crops grown in controlled environments, as building-integrated solar facilities, or as alternatives to high-impact PV for energy generation over agricultural or natural ecosystems.

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Agrivoltaic Farm Design: Vertical Bifacial vs. Tilted Monofacial Photovoltaic Panels

Collocating solar photovoltaic (PV) technology with agriculture is a promising approach towards dual land productivity that could locally fulfil growing food and energy demands particularly in rural areas. This ’agrivoltaic’ (AV) solution can be highly suitable for hot and arid climates where an optimized solar panel coverage could prevent excessive thermal stress during harsh weather thereby increasing the crop yield and lowering the water budget. One of the concerns with using standard fixed tilt solar array structure that faces north/south (N/S) direction for AV farming is the spatial heterogeneity in the daily sunlight distribution for crops and soil water contents, both of which could affect crop yield. Dynamic tilt control through a tracking system can eliminate this problem but could increase the system cost and complexity. Here, we investigate east/west (E/W) faced vertical bifacial panel structure for AV farming and show that this could provide a much better spatial homogeneity for daily sunlight distribution relative to the fixed tilt N/S faced PV structure implying a better suitability for monoculture cropping.

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Guide to Going Solar and Selecting Contractor

Montana Renewable Energy Association (MREA) gives steps, tips, and tricks to install solar at your home, businesses, farm or ranch, or school to save money on energy and increase your energy independence. Installing solar at your home, businesses, farm or ranch, or school will save you money on your energy bills and increase your energy independence. (1) Gather information: Do some research online and talk to the Montana Energy Office at the Dept. of Environmental Quality and a renewable energy advocate like the Montana Renewable Energy Association (MREA). A few questions to consider: Do you have a location on your property in mind already? Roof? Ground? Does the location get sun? Do you want to stay connected to the grid, or go off-grid? What is your budget for the project? (2) Contact local solar installers: Request bids from several installers to find the right fit and price for you. Ask for an in-person site visit to assess structural issues, electrical connections, and shading. Review historical energy usage to size the system properly. Discuss your energy goals. Do you want to cover all of your energy use or just some? (3) Review costs and financing: Does the cost meet your budget? Will you save as much as you were hoping on your energy bills? What tax credits are available to you? What loan or financing options are available? (4) Sign a contract: Once you’ve made your decision to move forward, contact your installer and sign a contract. Then, work can begin! (5) Installation: The timeline will depend on things like weather and the installer’s schedule, and inspection appointments. For net metering customers, expect additional time for the utility to install your net meter. (6) Start producing energy: Congratulations! Every kWh you produce is saving you money and increasing your energy independence.

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Gold on the Roof Economics of Rooftop Solar

This report compares the economics of a solar rooftop mandate for new detached residential homes with a conventional home with gas heating and central air-conditioning. The home with rooftop solar is assumed to be an all-electric, net-zero-energy home that would generate as much solar electricity on its rooftop each year as it uses. The gas-heated home would be built to the same standard in all respects other than the gas space and water heating and gas cooking are replaced by efficient electric devices in the net-zero-energy home. The context is Montgomery County’s 2017 ambitious climate emergency resolution and a more recent statement by County Executive Marc Elrich about the possibility of a rooftop solar mandate. The County’s goal is to reduce greenhouse gas emissions by 80% by 2027 and achieve 100% elimination of emissions by 2035

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Regional Climate Consequences of Large-Scale Cool Roof and Photovoltaic Array Deployment

Modifications to the surface albedo through the deployment of cool roofs and pavements (reflective materials) and photovoltaic arrays (low reflection) have the potential to change radiative forcing, surface temperatures, and regional weather patterns. In this work we investigate the regional climate and radiative effects of modifying surface albedo to mimic massive deployment of cool surfaces (roofs and pavements) and, separately, photovoltaic arrays across the United States. We use a fully coupled regional climate model, the Weather Research and Forecasting (WRF) model, to investigate feedbacks between surface albedo changes, surface temperature, precipitation and average cloud cover.

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The Regional Per-Capita Solar Electric Footprint for the United States

The potential resource base for PV in the United States is enormous; however, there are a number of challenges related to realizing this potential including relatively high cost, intermittent output, and potentially significant land use. The costs of PV have been declining significantly during the past couple of decades, and there are strong prospects for further declines in cost during the next decade. The issue of intermittency can be addressed through a number of potential means, and will likely become increasingly important as market penetration increases beyond a few percent of electricity consumption. The issue of land use is often cited as an important issue for renewable energy technologies. Determining the land requirements of solar PV at high penetration helps evaluate its potential to reduce both the carbon emissions and the “Ecological Footprint” associated with electricity generation and use.