Planning and Management of Solar Power from Space

By Panagiotis Kosmopoulos

Planning and Management of Solar Power from Space presents, for the first time, a holistic solar energy management and planning solution using Earth observation data and methodologies, giving an alternative view for precise electricity production and handling. Including examples of exploiting this solution by transmission and distribution system operators and solar power plants of both Photovoltaic (PV) and Concentrated Solar Power(CSP) systems, this book showcases real implementations and benefits of Earth observation technology, thus providing solar sector professionals an approach for continuously monitoring solar energy production and atmospheric parameter forecasts in high spatial and temporal resolution.

By guiding readers in tracking solar energy availability in relation to time horizons and forecasting, this book addresses potential challenges in research and development since this technology and the extensive use of such data and services enable accurate solar energy estimations and forecasts useful mainly in energy production control and grid stability.

• Includes state-of-the-art solar energy nowcasting technology based on radiative transfer model simulations, machine learning, computer vision, and Earth Observation input data
• Presents real examples of planning and management of solar power from space, including exploitation strategies from transmission and distribution system operators and solar energy plants production optimization
• Features spectral added value products and on-the-fly calculations for operational solutions

• Language: English
• Publisher: Academic Press
• Release date: Aug 31, 2023
• ISBN: 9780128235973

Panagiotis Kosmopoulos

Dr. Panagiotis Kosmopoulos is a Researcher at the Institute for Environmental Research and Sustainable Development of the National Observatory of Athens in Greece. He received his BSc in Geology and MSc in Environmental Physics from the National and Kapodistrian University of Athens and holds a PhD in Solar Radiation and Energy Forecasting from the Aristotle University of Thessaloniki. He has 20 years of professional experience through international projects and initiatives. He exploits Earth observations, big data, artificial intelligence, advanced graphic creation platforms, short- and long-term forecasting approaches and high-performance computing for renewable energy technologies, solar spectral irradiance studies, urban planning, aerosol and cloud physics, smart grids, and all-scale (from big solar farms to rooftop photovoltaic installations) solar plant management and planning. For more information, visit the Solar Energy Applications (Solea) webpage at http://solea.gr/.

Book preview

Chapter 1: Solar irradiance and exploitation of the Sun's power

Abstract

Climate change forces humanity to turn to sustainable and renewable energy sources and one of the most abundant is solar energy. The sun's radiation reaches the Earth's surface passing through a series of interferences due to airborne particles, clouds, and weather conditions, which have as result its reflection, scattering, and absorption. Photovoltaic (PV) systems is one of the most promising structures for the exploitation of solar energy. For the design, implementation, and efficient operation of these systems, the weather-dependent production plays a key role and determines the balance between production and demand. To enhance their efficient control and improve the accuracy of information on the availability of solar radiation, higher quality solar radiation data and validated forecasts are essential for planning and for deployment purposes. Modern technologies for solar energy conversion are mainly based in PV facilities and Concentrated Photovoltaic (CPV) facilities. The advantage of CPV over PV cells is that it is more cost-effective and has increased efficiency and higher daily productivity due to sun tracking. Another aspect, Concentrating Solar Power (CSP) technologies, which unlike PV technologies, do not use solar cells to generate current from solar energy. Instead, CSPs use mirrors or lenses to focus (concentrate) sunlight which is then converted into heat that creates steam and drives a turbine generating electrical power. Many studies have focused on the benchmarking of different approaches to forecast solar irradiance in different study areas and the aim behind all these studies was to predict operational solar energy. Clouds, aerosols, molecules, and dust are the main factors that new technologies, algorithms, and studies are trying to forecast and analyze in order to take full advantage of solar energy and the possibilities it provides.

Keywords

Aerosols; Clouds; Concentrated photovoltaics (CPV); Dust; Forecast; Photovoltaic (PV); Solar energy; Solar power; Solar radiation

1.1. Introduction

Among all the forms of renewable energy, solar energy is one of the most attractive forms due to its universal availability. About 50% of solar radiation lies in the visible part of the electromagnetic spectrum and remaining in the near-infrared portion. However, its availability is susceptible to weather disturbances. The solar radiation is subjected to reflection, scattering, and absorption by air molecules, clouds, and aerosols in the atmosphere. Clouds can block most of the direct radiation. Atmospheric aerosols not only scatter and absorb radiation but also affect the amount and lifetime of clouds. Predicting all these phenomena accurately is a very complex and difficult task. The effect of aerosols, dust, clouds, and fog on solar energy availability is still not properly understood and quantified. A single dust storm event may result in a quick blackout of sunlight and significantly affect the operation of a photovoltaic power plant (Mekhilef et al., 2012). Electrical utilities based on solar power generation use the solar irradiance incident on collectors, environmental factors, and many other specific system-design factors to estimate the electrical energy generated. Hence, the amount of solar power available to a conversion system is of crucial importance for scheduling, maintenance, and operation of solar-based generation systems.

The fifth assessment report of the Intergovernmental Panel for Climate Change (IPCC, 2013) concluded that the evidence for climate change is now incontrovertible and that a large part of this ongoing change is attributable to human activities, particularly due to the increased release of greenhouse gases (GHG) into the atmosphere. Several actions point to the fact that a more climate-resilient economy and society must be built in each country, including measures aimed at reducing fuel consumption for energy production, providing emphasis on energy efficiency and conservation, as well as on power generation from renewable sources such as the Sun and the wind.

Solar energy is the most abundant renewable resource and therefore much of the focus on sustainable energy is targeting in optimum solar energy exploitation (Szuromi et al., 2007). By 2050, the EU Energy Policy Plan (2011) aims to limit climate change by capping the global temperature rise to no more than 2°C (IEA, 2010). For this reason, the European Union (EU) provided the possibility for a reduction of GHG's emissions in the member countries by 80%–95% and hence established a goal of 20% of primary energy from renewable origin by 2020 (EU Energy Policy, 2011). In order to achieve this goal, the EU has laid out specific technology-roadmaps that will lead to the integration of low carbon energy technologies and in particular the deployment of Concentrated Solar Power plants (CSP) and Concentrated Photovoltaic (CPV) installations in the energy economy.

The energy source for any stand-alone photovoltaic (PV) system is the solar insolation available at the location of the installation. The performance of such a stand-alone PV system is directly affected by the amount of insolation available to the system (Kumar and Umanand, 2005). PV systems enable direct conversion of GHI into electricity through semi-conductor devices. Electricity from PV systems is expected to have a potential infrastructure of more than 200 GW by 2020 (EPRI, 2003). For the design, implementation, and efficient operation of these systems, the weather-dependent production plays a key role and determines the balance between production and demand. To enhance their efficient control and improve the accuracy of information on the availability of solar radiation, higher quality solar radiation data and validated forecasts are essential for planning and for deployment purposes. A major challenge is that forecasting the available insolation is not an easy task since it depends strongly on localized site-specific and complex weather conditions.

1.2. Basic information about solar radiation and the potential to exploit its power

The radiant flux reaching the surface of the Earth is termed as solar irradiance which is expressed in W/m². The Global Horizontal Irradiance (GHI) is the sum of Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI), and ground-reflected radiation. However, because ground-reflected radiation is usually insignificant compared to direct and diffuse, for all practical purposes global radiation is said to be the sum of direct and diffuse radiation only:

Equation 1.1. (1.1)

where Equation is the solar zenith angle (Figs. 1.1–1.2).

Figure 1.1  Solar geometry on a tilted surface.  Credits: P.Kosmopoulos.

Figure 1.2  Components of solar irradiance on a tilted surface.  Credits: Miguel De Simón-Martín.

The Direct Normal Irradiance (DNI) is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the Sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the Sun. The total direct insolation (Dirtot) for a given location is the sum of the direct insolation Equation from all Sun map sectors:

Equation 1.2. (1.2)

The direct insolation from the Sun map sector ( Equation ) with a centroid at zenith angle (ϴ) and azimuth angle ( α ) is calculated using the following equation:

Equation 1.3.

(1.3)

where Equation is the solar flux outside the atmosphere at mean Earth-Sun distance, known as solar constant. The solar constant generally used is 1367 W/m², which is consistent with the World Radiation Center (WRC) solar constant. β is the transmissivity of the atmosphere (averaged over all wavelengths) for the shortest path (in the direction of the zenith). Equation is the relative optical path length, measured as a proportion relative to the zenith path length (see Eq. (1.4) below). Equation is the time duration represented by the sky sector. For most sectors, it is equal to the day interval (for example, a month) multiplied by the hour interval (for example, a half hour). For partial sectors (near the horizon), the duration is calculated using spherical geometry. Equation is the gap fraction for the Sun map sector. Equation is the angle of incidence between the centroid of the sky sector and the axis normal to the surface (see Eq. (1.5) below).

The relative optical length, m(θ), is determined by the solar zenith angle and elevation above sea level. For zenith angles less than 80°, it can be calculated using the Eq. (1.4):

Equation 1.4.

(1.4)

where Equation is the solar zenith angle and Equation is the elevation above sea level in meters.The effect of surface orientation is taken into account by multiplying by the cosine of the angle of incidence. Angle of incidence ( Equation between the intercepting surface and a given sky sector with a centroid at zenith angle and azimuth angle is calculated using the following equation:

Equation 1.5.

(1.5)

where Equation is the surface zenith angle (note that for zenith angles greater than 80°, refraction is important) and Equation is the surface azimuth angle. For each sky sector, the diffuse horizontal irradiance (DHI) at its centroid is calculated, integrated over the time interval, and corrected by the gap fraction and angle of incidence using the following equation:

Equation 1.6.

(1.6)

where Equation is the global normal radiation (see equation g below) and Equation is the proportion of global normal radiation flux that is diffused which is approximately 0.2 for very clear sky conditions and 0.7 for very cloudy sky conditions. Equation is the time interval for analysis and Equation is the gap fraction (proportion of visible sky) for the sky sector. Equation is the proportion of diffuse radiation originating in a given sky sector relative to all sectors (see Eq. (1.8) below) and Equation is the angle of incidence between the centroid of the sky sector and the intercepting