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Concentrated photovoltaic solar panels. What is Concentrated Solar Power?

Concentrated photovoltaic solar panels. What is Concentrated Solar Power?

    Cheapest is not always best: Concentrated solar power could beat lower price PV with new market rules

    CSP can deliver greater grid stability than photovoltaics, but needs better recognition of its value to be competitive.

    Concentrated solar power’s failure to gain momentum in U.S. markets is a signal that traditional resource valuations may be slowing the energy transition, a February CSP conference made clear.

    CSP. which converts the sun’s heat to electricity, was once dominant, then faded when photovoltaic (PV) solar, which turns the sun’s light into electricity, plummeted in price. But unlike CSP, PV, even with batteries, cannot provide the long-duration, dispatchable generation that high-renewables power systems will need. conference participants said.

    Renewables are now mainstream and fossil fuels are the alternative, California Energy Commission (CEC) Chair David Hochschild told regulators, utility executives and analysts at the conference. With new zero-emissions mandates, we will need a diversity of renewable resources to keep the system reliable, and we will need CSP, particularly, because of its long duration storage [potential].

    Ambitious 100% renewables mandates drive indiscriminate procurement of the lowest-cost renewable kWh, utility executives and regulators said. But the transitioning power system requires broader value. even if the per-kWh price is higher.

    Restructuring markets, policies and utility planning to compensate investments in resources with a higher overall grid value, despite higher capital expenditures, will be necessary to deliver a reliable, low carbon power system, they added.

    How CSP works

    CSP uses mirrors to concentrate the sun’s heat within a single point containing a heat-retaining fluid. The captured heat creates steam that, like conventional generators, drives an electricity-generating turbine.

    CSP tower technologies, like the 110 MW Crescent Dunes Nevada project and the 394 MW Ivanpah California project. FOCUS the sun’s heat on fluid flowing through a tower’s apex. Trough technologies, like the 280 MW Solana project in Arizona. heat liquid flowing through the focal points of trough-shaped mirrors.

    Heat-absorbing fluids include water, as at Ivanpah, or a molten liquid that more efficiently holds heat, as at Crescent Dunes. Insulated tanks store the heated fluid for on-demand dispatch of electricity.

    Utility-scale PV panels release electrons when exposed to the sun’s light. The electricity flows to the grid or can be stored in batteries. Cost and regulatory barriers have largely limited cost-effective battery storage to four-hour durations, although battery stacks and alternative battery chemistries that deliver longer duration storage have been piloted.

    In 2010, the U.S. had 0.4 GW of CSP and only 0.1 GW of utility-scale PV. But cumulative CSP installations reached only 1.7 GW by 2020, while falling panel costs led to the installation of 35.4 GW of utility-scale PV by 2020, Wood Mackenzie Senior Analyst for U.S. utility-scale solar Colin Smith emailed Utility Dive.

    Since 2014, CSP technology has been plagued with performance problems and a high price point, Smith said. It has had trouble competing with PV or PV plus storage, even with the promise of 12-hour-to-24-hour continuous power.

    Globally, policy incentives as well as high electricity have kept CSP’s high capital and per-kWh costs from being a barrier. At the end of 2019, 90 CSP plants representing about 6,000 MW of capacity were in operation around the world. Hank Price, managing director of CSP developer Solar Dynamics, told Utility Dive.

    Questions about CSP grew in the U.S. after Crescent Dunes’ contract with Nevada’s NV Energy was canceled in 2019 due to flaws in the molten salt storage system. But other countries have found success with that storage method — six of the 14 global tower projects and over 30 trough projects use molten salt fluid for storage.

    Repairs are reportedly underway for NV Energy and the project will likely find another off-taker, Price said.

    But many at the conference told Utility Dive that doubts about CSP’s technical feasibility and the low cost of PV could make a new contract difficult to find. NV Energy declined to comment.

    CSP’s first barrier: Getting paid

    Early CSP projects had capital costs that reached billions of dollars and their average levelized cost of energy (LCOE) was

    Better modeling and planning

    The modeling done for integrated resource planning can identify the higher value of CSP and other low-carbon technologies that offsets its higher costs, National Renewable Energy Laboratory (NREL) Senior Analyst Trieu Mai told Utility Dive. Portfolios can then be re-evaluated with production cost modeling for reliability and resource adequacy in an iterative process.

    The models consider essentially infinite options to make tough choices about how the system operates today and how it might operate in the future, he said.

    Variable wind and solar interconnected with the grid through inverters can cause fluctuations in voltages and frequencies that create challenges for protecting system stability. power system consultant Debra Lew, a former NREL Engineer and GE Technical Director, told Utility Dive. But there is a future coming with a lot of variable wind and solar. and there has not been sufficient planning for that future.

    Work on using zero-emissions resources not interconnected through inverters to meet capacity and system balancing needs is advancing, but work on using them for system stability is not, she said. Instead, system operators are investing in hardware to correct and react to voltage and frequency fluctuations.

    Zero-emission dispatchable resources like CSP, stored hydro, and geothermal can provide system stability and offer more value than a utility investment in hardware, because the utility gets clean energy with the expenditure for system stability, Lew said. But there are few incentives or market mechanisms to compensate utilities and developers for those investments, so PV and batteries will be built because they are cheap and fast and hardware will remain the main tool for system stability.

    CSP’s second barrier: Short-term thinking

    In the future, planners may have supermodels that identify long-term value in high capital expenditures, but today’s models often lead to short-term solutions, Lew said. The alternative is to identify what resources will be needed in zero emissions scenarios and build them now, but that would require the long-term planning we are not doing.

    The size of investment in resources like CSP and the time it takes to develop them are also very daunting for a regulated utility, Arizona Public Service (APS) Vice President for Public Policy Barbara Lockwood told the conference.

    There are many new uncertainties about demand because of the emergence of new load serving entities (LSEs) and rapidly increasing customer adoption of distributed resources and energy efficiency, she said. As a result, APS has defaulted to much smaller investments like small PV plus storage installations that require lower capital expenditures and shorter times to develop.

    Southern California Edison (SCE), in response to similar market signals, has also shifted procurement away from high capital expenditures, said SCE VP for Energy Procurement Bill Walsh. Smaller procurements help control or smooth the system or fill in gaps as generation changes.

    Utilities prefer the incrementalism of [requests for proposals] for 50 MW or 100 MW investments because it seems less risky, former Nevada commissioner Wagner said. But that is short-term thinking and avoids evaluating and recognizing system needs over the longer term. To achieve 100% clean energy goals. we need to start thinking out of the box and explore all opportunities.

    Electric utilities are moving from what resource we want to what service we need and when we need it and more suitable contracts might be more about capacity than about energy, APS’s Lockwood agreed.

    Electrification and zero emissions mandates could increase the California system’s load by 75% or more and that will require big investments in new generation, California Independent System Operator CEO Steve Berberich told Utility Dive. Counterparties, like investor owned utilities and new LSEs, for those investments should be part of designing new contracts that can secure the capital needed.

    Contracts must support projects that offer services from renewables that we got from the thermal fleet, Berberich said. A new accounting process being developed by California regulators should lead to metrics that can be used for those contracts, he added.

    concentrated, photovoltaic, solar, panels, power

    Value is becoming a key part of planning, California Public Utilities Commission (CPUC) Energy Division Head Edward Randolph told Utility Dive.

    The effective load carrying capacity of PV without storage was set at 17% in a 2019 CPUC ruling, which means only 17 MW of a 100 MW solar procurement counts toward meeting peak demand. That will likely increase procurements of resources that can better meet system peaks.

    That type of fundamental rethinking of what system value is and how to define it quantitatively is needed for zero carbon resources with high upfront capital costs, Aggarwal said.

    .21/kWh. Although the upfront capital cost is still high, the U.S. Department of Energy estimated CSP’s 2018 LCOE, with 12 hours of storage, dropped to.098/kWh.

    A 2019 contract price for CSP with storage in Dubai was reported at.083/kWh. significantly less than the Lazard-reported LCOE of.15/kWh or more for a natural gas peaker plant that its flexibility would allow it to replace.

    Monetizing CSP will require new incentives that value its unique set of system benefits instead of valuing the least cost resource, former Nevada utility commissioner Rebecca Wagner told Utility Dive. Advocates need to make the case to regulators that CSP may cost more, but its storage allows using renewables overgeneration to flatten peak demand and fill gaps when wind or PV are not producing.

    If CSP advocates make that case, regulators will need to reconsider existing market rules and regulatory structures, according to analysts at the conference.

    Markets and regulatory structures were set up around a different set of electricity resources than those that will dominate the future, Energy Innovation VP Sonia Aggarwal told Utility Dive at the conference. That has cascading implications.

    Existing incentives assure compensation to a generation source for the value its energy delivers to the power system in cents per kWh, Center for Energy Efficiency and Renewable Technologies (CEERT) Senior Technical Consultant Jim Caldwell told Utility Dive. If CSP got paid for all its services, it might be able to compete, but that would require different market rules.

    CSP could play a role in controlling the rising cost to ratepayers of meeting peak demand ramps, but market rules define procurement separately by energy, capacity and ancillary services, Caldwell said. CSP doesn’t win in separate solicitations. Only pricing all three together makes CSP the least cost solution, especially now because capacity and ancillary services are becoming more valuable.

    The need to accurately value the services resources deliver is an emerging challenge for system operators across the country, Caldwell said. It’s premature to value specific services now, and it might be inaccurate because the need for them is still limited, but it’s not too early to think about how we value them so the method is ready when it is needed.

    Concentrated photovoltaic solar panels

    Universities Private Sector

    For mobile, landscape view is recommended.

    Soitec constructed a (1) MWAC power plant (“Project”) at the U.S. Army’s installation at Fort Irwin, California, to demonstrate the Concentrix® (CX) concentrating photovoltaic (CPV) technology and address the Environmental Security Technology Certification Program’s (ESTCP’s) objective of cost effective on-site distributed energy generation. The Project employed 40 Soitec CX-S530 CPV systems and included third party performance validation by the National Renewable Energy Laboratory (NREL) and solar forecasting development expertise by the University of California at San Diego (UCSD). The data collection and observation period ran from 28 July 2015 to 28 July 2017 (24 months). The Project’s objectives were to demonstrate to the Department of Defense (DoD) the reliability and cost-effectiveness of the CPV technology in a harsh desert climate with high Direct Normal Irradiance (DNI, which means direct sunlight) a majority of the year. Additionally, the solar forecasting system, a component of the Project, was intended to produce a direct, measurable benefit to the DoD by providing cost-effective ways to manage and distribute on-site solar generation, resulting in increased energy quality and security.

    Technology Description

    CPV technology converts sunlight into electricity with state-of-the-art Fresnel silicone on glass lenses concentrating sunlight onto high performance multi-junction solar cells. The modules are mounted on dual axis trackers that follow the sun’s trajectory throughout the day. Fresnel lenses concentrate the sun by a factor of approximately 500 onto a small solar cell, thereby reducing the size and amount of costly cell material required.

    Specific demonstration objectives and results are show in the table below.

    Implementation Issues

    • Dual-axis drive. The drive unit, though composed of a standard housing, slewing rings, worm gearing, reduction gearboxes and alternating current (AC) motors, was source of end-user concern. Major worries were how the drive would handle the large tracker loads (especially during wind or seismic events), if the drive’s precision would support the exact pointing requirements of the CPV tracker (especially over time as the gear teeth experienced wear), and the general lifecycle of the drive.
    • Soitec’s Long-Term Viability. End users, developers and investors were concerned about what would happen if Soitec went bankrupt or abandoned its solar business.
    • Equipment and Implementation Costs. Equipment costs for this Project were over 450.20/watt. During the same time period, conventional PV module efficiency rose moderately and fell precipitously. Support technologies, such as 3rd party single-axis trackers and inverters have seen a shakeout in the industry, with quality rising and falling.
    • Operations and Maintenance (OM) Costs. End-users were concerned at the lack of real OM cost data, realizing that the CPV technology was unproven and could require intensive preventive and reactive maintenance over the life of the plant.
    • Lack of Commercialization of CPV System Components. At the time of construction of the DoD Fort Irwin project, the Soitec Bill of Materials were a combination of standard commercial off-the-shelf items, custom-built parts, or newly commercialized parts.

    In 2015, Soitec announced its exit of the solar business and began the divestiture process. In late 2016, Soitec sold its CPV technology to Saint-Augustin Canada Electric Inc. (STACE), a worldclass supplier of large electrical equipment in the power generation industry. With this acquisition, STACE became the technological leader of the CPV industry and stated it would continue to improve the technology and maintain the collaboration with the recognized Fraunhofer Institute for Solar Energy Systems ISE, based in Freiburg, Germany.

    Principal Investigator

    Soitec Solar Phone: 858-888-3137

    New Progress in TI-CPV

    The categories of systems surveyed in this section will be organized similarly to the review of Apostoleris et al. (2016), with each section spanning a range of developments from design concepts to fully realized pre-commercial modules.

    Beam Steering

    A number of advancements in broad-Band beam-steering systems have been realized in recent years; these can be used not only as tracking systems for solar concentrators but also for other systems such as Smart Windows or skylights. Electrowetting-based liquid prism beam steering systems represent the one major area where non-mechanical approaches to sun tracking have seen development. The most traditional beam steering mechanism is visualized in Figures 1A,B.

    FIGURE 1. Evolution of electrowetting-based beam-steering tracker concepts, from (A) an array of simple EW prisms with a single water-oil interface, modifying the propagation angle of sunlight to (B) maintain uniform illumination of a Fresnel lens, to (C) independent control of the voltage and consequent wetting angle in each prism to achieve simultaneous beam steering concentration without the need of a separate concentrating lens (Khan et al., 2020); and (D) realization of larger steering angles by use of a compound prism with two interfaces between three different immiscible liquids (Chen et al., 2021).

    Khan et al. (2020) designed a two-axis beam steering hexagonal cell array that eliminates the need of further concentration by a Fresnel lens, as shown in Figure 1C. Compared to a square cell, a hexagonal shape attains a slightly higher “fill factor” and encourages higher degrees of freedom in controlling its rotation. The fill factor in this context (distinct from the photovoltaic IV curve parameter) is the distance between opposite faces of the cell for a fixed volume and thickness. CFD simulation using the Laminar Two-phase Flow Moving Mesh (LTPFMM) module of COMSOL Multiphysics software and experimental tests show that applying 26 V to one of the electrodes in the cell caused a maximum contact angle of 44°. over, a small difference of 0.2 in the refractive indices of the fluids revealed a 4.5° deflection in path. The same authors provided additional review of the latest technologies and research utilizing electrowetting-controlled liquid lenses for solar beam steering (Khan et al., 2017), detailing the process and components with insight onto the future possibilities and guidelines on design and component selection.

    Chen et al. (2021) developed a programmable beam-steering compound prism (PCP) powered by a triboelectric nanogenerator (TENG) and a resistance-capacitor (RC) circuit that converts AC output signal from the TENG into DC to eliminate the additional costs and maintenance of a DC power supply. The RC circuit controls the prism angle by changing the resistance which in turn modifies the applied voltage. The DC voltage is required to activate the interface between two oils and water in the prism (Figure 1D) and cause the deflection of sunlight. The steered, now perpendicular, light is then concentrated onto a multi-junction cell by a Fresnel lens. The proposed design was able to steer light at an acceptance incident angle of 15° which is 38% higher than conventional single prisms. Strong concentration was seen as the power collected by the multijunction cell increased to 1.288 mW from 0.088 mW in the case of its absence.

    Mechanical approaches to beam steering have been demonstrated as well with (Johnsen et al., 2020) developing a method for optimizing the optical design of lens-based beam steering arrays which are adjusted by mechanically shifting the different optical layers relative to each other. In this regard the approach has commonalities with what has come to be called micro-tracking, which represents the largest area of activity in the tracking-integration space.


    Price et al. (2017) demonstrated a high-performance planar micro-tracking CPV minimodule based on their previously presented concept of combining refractive and reflective optics to achieve image-field flattening. The design in Figure 2A entails a catadioptric stack which consists of a planoconvex top refractive and bottom reflective optics sandwiching a central glass sheet at which a 3J microscale cell is placed. The glass sheet laterally slides between the optics using an index-matching oil and is controlled by a microcontroller running an algorithm derived from feedback of the measured short-circuit current. Optical efficiency exceeds 90% at 0° angles of incidence and begins dropping beyond 70° at a practical concentration that ranges between ×300 and ×400 with standard optical materials and up to ×660 with higher index optics. The electrical conversion efficiency remains around 30% between 10:00 and 14:00 in outdoor testing and exhibits a lower efficiency than the bare 3J cell due to cell heating (cell heating, a persistent challenge for CPV, can be significantly reduced by moving towards a “micro-CPV” paradigm in which sub-mm cells are utilized to boost heat dissipation from the edge (Domínguez et al., 2017). This performance approaches that predicted by (Grede et al., 2016) in the same group, who established a phase space procedure to optimize planar micro-tracking CPV, discussed its thermodynamic limits and provided design guidelines for such systems along with the practical limits induced by absorption and dispersion.

    Modeling TI-CPV Performance

    Model Description

    In order to evaluate TI-CPV performance accurately, it is necessary to go beyond raw figures such as efficiency and consider the interaction with the full solar resource in the location and over the time period of interest—in other words, to implement a performance model. Companies developing TI-CPV products have developed their own modeling tools which are specific to their products, and furthermore are typically proprietary and as such of limited use to the general research community. Nardin et al. (2020) described a modeling approach for general TI-CPV systems in the Python PVLIB framework, which uses a single-diode model for both CPV and PV components of a hybrid system as described in the previous section, adding correction factors for temperature and spectral impacts on optical performance. This model was validated with real-world data from outdoor tests of Insolight’s modules at Madrid Polytechnic University and is under continued development as a high-accuracy modeling tool.

    In the past, the present authors have used a scaled-down performance modeling methodology for “ballpark” estimates and particularly for comparison to established PV technologies. Intended for ease of use, the electrical performance model is semi-empirical model and depends only on the plane-of-array direct irradiance and direct light incidence angle, in addition to the solar-to-electric efficiency as a function of the incidence angle. This is often approximated as a step function characterized by a single efficiency, typically measured at normal incidence, and a maximum tracking angle. All parameters should be measured under “real” conditions to the extent possible—e.g., use an outdoor measurement of efficiency, in a climate similar to that where it will be deployed, rather than one at standard test conditions. For more accurate modeling and extrapolation to other climates, factors to account for ambient temperature and spectral variations should be included; accurately evaluating these is the subject of ongoing work. The same approach can be taken to evaluating light-splitting hybrid systems—either CPV-PV or semi-transparent CPV.

    These semi-empirical models can be “built up” in four stages, which can be implemented depending on the resolution of the available environmental data and the number of system parameters that can be defined. The “first pass” model, used for very rough estimations, simply separates the direct and diffuse components, where the direct is converted with a constant efficiency η and the diffuse is transmitted with a constant transmittance τ. This does not account for angle-of-incidence, spectral or thermal effects, but this can be roughly compensated by appropriate definition of the τ and η. The “second pass” model requires solar irradiance data of hourly or greater resolution, including the angle of incidence of the direct component on the plane of array. The power output and light transmittance is calculated for each timestep based on three parameters: η, τ and the maximum tracking angle θtrack, where the electrical power output Pel is given by:

    And the transmitted optical power is approximated by

    concentrated, photovoltaic, solar, panels, power

    A third-pass model would evaluate the functions η(θ), τ(θ) and τdiffuse (which is simply the appropriately weighted integral of τ(θ)) and evaluate the instantaneous electrical and optical power outputs under a prescribed operation mode [which may optimize electrical power generation (E-mode) or alternate between power generation and maximizing light transmission (MLT-mode)]. To calculate the instantaneous efficiency of the module at each incidence angle stamp, the power factor, as in the value of power relative to the power at 0° incidence angle, is multiplied with the constant efficiency value used in first and second passes. The power factor is extracted from graphs generated by the manufacturer that have been corrected to account for cosine projection. The electric power generated takes into account the ambient temperature effects, in which within the tracking range:

    in which T c e l l is calculated by adding the instantaneous T a m b i e n t to a constant temperature offset Δ T representing the average experimental temperature difference between the cell and the ambient.

    The transmittance is a bit more complicated as it differs between the E-mode and MLT- mode, as shown in Table 2.

    TABLE 2. Transmittance at different modes.

    To clarify, in E-mode, within the tracking range, none of the beams impinging at the plane of array affect the transmittance as opposed to the diffuse component which is assumed to be transmitted at a constant τ as in the first and second passes of the model. All other values of direct component transmittance are calculated as a function of angle of incidence using graphs generated by the manufacturer. The transmitted power is then the sum of the direct and diffuse transmitted irradiance.

    Economic Considerations

    One thing that has become clear is that future economic value from CPV systems will not come from a (typically modest) boost in electrical output alone, but in the division of the solar resource into multiple output streams (e.g. heat, light, electricity) as recently described by several of the present authors (Apostoleris et al., 2021a). To evaluate the economic potential of these systems requires a slightly more involved computation than the familiar LCOE estimation, although the same underlying equation applies. To illustrate, a semi-transmissive CPV module is considered based on that demonstrated by Insolight, which splits light between an electrical and a transmitted light component. The results of the third-pass model are used implemented expressing the output electric power in kW/m 2 of module and the transmitted light in lumens/m 2 of module. This procedure indicates a first-year electrical output of 317.3 kWh/m 2 and 59.4 million lumen-hours/m 2 of module optically. From Figure 8, it can be seen that the optical power is around 2.5 times this value if the module is operating in MLT mode since the full GHI resource is used for transmission.

    To evaluate the overall economic potential of this system, it is necessary to assign values to each of the two output streams. The value of the transmitted light depends on how it is utilized. In a building-integrated setting the transmitted light is assumed to be used for daylighting, where standard recommended lighting levels (500–1,000 lux) are an order of magnitude lower than the light transmitted through the module. Over a year, one square meter of module at 20° tilt transmits roughly 63,500,000 lumen-hours under Abu Dhabi weather conditions. If the entirety of this light can be used for daylighting and offsets artificial light, 600–1,200 kWh of lighting energy are avoided per year, if that light would otherwise be provided by LED lamps with 50–100 lumen/W luminous efficacy—exceeding the energy produced by the module itself. The transmitted light, if it can be used to offset artificial lighting, effectively doubles the output of the module if both generated and avoided electricity are counted. Since this light is only available while the sun is shining, it can treated as displacing solar electricity with the same value in c/kWh.

    The value of the electrical output is straightforwardly given by the price at which the electricity can be sold—in sunny parts of the world. For this study, the price of electricity was set equal to the LCOE of the PV module using the equation below:

    where C is the CapEx in (/kW), Oy is the operating cost in year y, r is the discount rate, Egen is the electricity generated, and L is the system lifetime.

    Setting a CapEx of 920 /kW to account for EPC (equipment, design, labor, etc.) as per NREL’s benchmark for commercial rooftops PV systems, operating costs scaled up at a 2% of the CapEx yearly, a discount rate equal to the project internal rate of return (∼4%), a lifetime of 25 years, and the power generated by the PV module in the model the LCOE is 4.2 c/kWh which is a reasonable or even conservative value for when-generated solar electricity, as generation costs contract have dropped rapidly in recent years. In previous work (Apostoleris et al., 2021b), it was shown that large-scale photovoltaic installations in the Gulf region can achieve generation costs of 3 c/kWh at capital costs of ∼450/W and operating costs of 10/kW annual with an IRR of ∼4%.

    A generally applicable metric (Apostoleris and Chiesa, 2019) for evaluating the economic potential of an energy (or other infrastructure) investment is the net present value (NPV) taken as the sum of all discounted revenues minus the sum of all discounted costs. As the transmitted light has already been converted into units of electricity consumption avoided, the NPV can be expressed as:

    N P V = P e l ( ∑ y = 1 L E g e n ( 1 r ) y ∑ y = 1 L E a v ( 1 r ) y ) − ∑ y = 1 L O y ( 1 r ) y − C ( 7 )

    where Pel is the electricity price (assuming the same price for generated and avoided electricity) and Eav is the avoided electricity consumption.

    Without deeply considering the specific contexts in which TI-CPV would be deployed, the module cost premium that could be tolerated if all output streams are fully utilized and other costs remain unchanged can be considered. The LCOE now represents the minimum sustainable price of electricity and a worst-case, conserved scenario of 100 lumens/W luminous efficacy (LED) for the electricity avoided by the transmitted light is set. In Figure 10, the NPV under these conditions is displayed as a function of system price, given in USD per m 2 of module on the lower x-axis and the equivalent USD/W for a 20% efficient conventional PV module array on the upper x-axis. This rough analysis suggests that a cost premium in excess of 965/m 2 could be tolerated under these conditions. If all of this additional cost were concentrated in the module, that would represent a maximum viable module price roughly more than triple that of a conventional Si module. The overall increase in solar resource utilization should be owed to the mixed effect of integrated tracking and the transmissive behaviour of the module.

    Discussion Outlook

    While interesting concepts in tracking integration have proliferated in recent years, mechanical micro-tracking has seen the most advanced demonstration and has made the most progress towards commercialization. CPV systems adopting integrated tracking and diffuse collection are able to provide multiple output streams in conjunction with electricity like daylight and heat simultaneously.

    A number of technical challenges must be addressed in order to realize commercially viable TI-CPV modules. The concept at which the tracking motion is triggered needs to be reliable and prompt since it affects the overall performance. Predominantly in small cells, any minor misalignment or a lagging reaction to the point of array’s incident angle will waste the potential of irradiance accumulation.

    Therefore, one design feature that requires more FOCUS is the alignment error between the cell array and the lenses. A study by study by José et al. (2020) explains a method to characterize the misalignments for micro-CPVs and quantify them in metric values as distance between centres. The process starts with capturing a magnified image of the receiver with a camera followed by pre-processing the image like increasing its contrast. Then, the images are segmented on MATLAB using Superpixel Oversegmentation and Fast Marching Method. Finally, Hough Transform helps realise the circles’ pixels. over, depending on the acceptance angle limits, the rate at which trackers respond to the change in incidence angle and actuate has a considerable effect on the power production yield and heating of the cell.

    Programmable techniques in micro-CPVs are promising towards preventing these mishaps. One technique is calculating the incidence angle at each timestamp based on the geographical location, date, and tilt angle then establishing the tracking movement accordingly when the incidence angle lies within the tracking range. In addition to that, another concept is predicting the maximum power production at each timestamp and acquiring the exact coordinates of the cells relative to the optics needed to realize that power. The limitation to this approach is that the tracking process will cease to function as expected in an event of a disrupted load cycle, as experienced in the experimental characterization of the Insolight module. The different tracking modes available can be efficiently used to serve different applications. While it might seem unwise to acquire a CPV module to operate it in MLT-mode (Maximum Light Transmission), an optimized switching behaviour between it and E-mode (electrical generation) can help in regulating the transmitted light in agriculture and daylighting applications or keeping it constant throughout the day albeit the incidence angle. In the case of low direct light irradiance, contrary to typical CPV modules with no silicon cells in the back-pane, the solar resource would still be utilized for transmission. In agriculture, some plants require a certain level of instantaneous PAR (Photosynthetically Active Radiation) or a constant total accumulated level daily to flourish. In daylighting, it would be preferable to maintain a regulated level of light in lumens/m 2 at all times of the day when sunlight is available. In both applications, it’s worth noting that this switching mechanism also has an effect on the temperature within.

    The location and application of the TI-CPV module need to be taken into consideration during the manufacturing and material selection process. From “big league” components like the top glass pane to “small fry” components like the glue between the lenses in an array, the environmental conditions like temperature, sand, and humidity need to be taken into consideration. The glue between the lenses should withstand the ambient temperature or else its melting behaviour would cause disintegration of the lens array or clinging of sand and dust which would ultimately decrease the aperture area. Regarding the top pane, a flat glass surface would protect the optics from soiling and provide an undemanding cleaning routine, considering that it should not largely affect the intensity of transmitted irradiance. Another undermined parameter that could facilitate the commercialization of the modules is the weight of the module frame, especially in roofing greenhouses and buildings.

    A particular challenge has been the trade-off between the concentration factor and the tracking range. Actually realized TI-CPV systems have simultaneously achieved tracking angles in excess of ±50° with concentration factors around ×200. However, this concentration is roughly ×2 lower than what is needed to make III-V multijunction cells, which are required to achieve the performance assumed in the preceding analyses, economically feasible to use. While continued research development to boost the performance of tracking-integrated optical systems continues, advances in multijunction cell production—such as a breakthrough in the long-sought goal of III-V wafer reuse, or the development of a stable, high-efficiency perovskite-on-silicon multijunction—could represent a critical development that would transform the economics of TI-CPV.

    What is the difference between CSP and Concentrator Photovoltaics (CPV)?

    The two systems may appear to be the same but each uses different technologies. Concentrator photovoltaics converts the sunlight into electricity through PV cells made of semiconductor materials.

    While the photovoltaic effect comes into play in one, the other system (CSP) uses different principles, such as the heat-transfer fluid.

    What are the disadvantages of concentrated solar power?

    When we talk about the disadvantages involving CSP, it is common to list the high complexity of installation and its high cost. And it’s true, but whenever we bring up these items, it’s within the context of comparison with photovoltaic systems.

    And therein lies the error. Because, as it is a thermal energy, the correct thing would be to compare it with other thermal energy sources, such as natural gas.

    What are the advantages of concentrated solar power?

    We are talking about an energy whose source is the sunlight, that is, a free and abundant resource. And just like natural gas, CSP is also dispatchable.

    Despite being a clean and renewable source, Concentrated solar power still lags behind natural gas when it comes to price.

    But here we have a problem, as affordable as natural gas is, we are talking about an energy source that ends up leaking methane – this greenhouse gas is way more potent than carbon dioxide.

    Therefore, CSP is far from being seen as a disposable or low-potential energy source. Its potential gains even more supporters when we see that this system can complement photovoltaic systems and thus help leverage the solar and wind industry.

    Source: Frame Stock Footage/Shutterstock

    Is Concentrated Solar Power becoming cheaper?

    This is an excellent prospect that solar energy technology has shown over the years. Just as the cost of photovoltaic panels has dropped, the cost of installing CSP has also decreased – from 2019 to 2020, there has been an 18% reduction in price.

    CSP Trending Companies in recent years

    According to Vantage Market Research, the concentrated solar power market size is estimated at nearly USD 50 billion (2021). For the year 2050, forecasts indicate that the market could reach almost USD 60 billion.

    Faced with the potential of technology and global efforts like the Paris Agreement, many venture capitalists have invested in companies responsible for shaping this solar energy niche.

    Many of these companies like SolarSteam and Tewer Engineering work with their own software and with their own heliostats configuration. The sector, as shown below, is already spread across different continents.

    This new market has benefited from the know-how of other industries such as mobility/automotive through talent acquisition. Many engineering professionals are transitioning into the energy industry, thereby increasing expertise in the renewables sector.

    Some countries are already taking the lead. Investments in developing a high-skilled workforce and the ready energy infrastructure are two factors pushing the results in solar power to its maximum.

    We can help with your energy transition

    We at Airswift recognised experience in the most diverse energy sectors. We work closely with companies of all sizes to become less dependent on fossil fuels and then leading the energy transition underway.

    With more than 60 offices globally and over 7,000 contractors, we have a database full of the most skilled STEM talent to help expand your business.

    Want more insight into talent trends in the technology industry? Click the link below to download our latest whitepaper.

    This post was written by: Raphael Santos, Content Marketing Coordinator

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