Possible advances in Solar Technology

“Massive expansion of solar generation worldwide
by mid-century is likely a necessary component
of any serious strategy to mitigate climate
change. Fortunately, the solar resource dwarfs
current and projected future electricity demand.

In recent years, solar costs have fallen substantially
and installed capacity has grown very
rapidly. Even so, solar energy today accounts for
only about 1% of U.S. and global electricity
generation. Particularly if a substantial price
is not put on carbon dioxide emissions, expanding
solar output to the level appropriate to the
climate challenge likely will not be possible
at tolerable cost without signifi cant changes
in government policies. ” Source: “The Future of Solar Power”, Energy Initiative
Massachusetts Institute of Technology, Copyright © 2015 Massachusetts Institute of Technology All rights reserved.

In this era of the transitional energy technology cusp, what we need now and what we will use to generate power in future are two very different things. Some say current technology, including battery technology, is all we need. I disagree. Here are some promising advances in solar technology which may light our future, but which at the current time are still in development.

Due to the actual state of technology today I have no objection to the deployment of new generation clean coal power generation. This is a far better interim solution for Australia than nuclear power, for reasons outlined in previous posts and in the next post to come.

Technion Israel – Advanced efficiency solar panels via optimised light frequency re-radiation. Promises 70% conversion efficiency

“New Technology Aims to Makes Photovoltaic Cells 70% More Effective

Technion researchers have developed a technology that could improve the efficiency of photovoltaic cells by nearly 70 percent. The study was conducted at the Excitonics Lab, headed by Assistant Professor Carmel Rotschild at the Faculty of Mechanical Engineering, with the assistance of the Grand Technion Energy Program (GTEP) and the Russell Berrie Nanotechnology Institute (RBNI) at the Technion, and as part of the lab’s ERC project on new thermodynamic tools for solar cells.

The sun is a powerful source of renewable energy. In fact, it is currently the only energy source capable of supplying the energy consumption of the human race, so it’s no wonder that the use of solar energy is increasing. But there are currently a number of technological limitations when it comes to photovoltaic cell efficiency.

Photovoltaic cells optimally utilize a very narrow range of the solar spectrum – the broad light supplied by the sun; radiation not within this narrow range merely warms these cells and is not utilized. This energy loss limits the maximum efficiency of current solar cells to around 30%.

The Technion team’s method is based on an intermediate process that occurs between sunlight and the photovoltaic cell. The photoluminescence material they created absorbs the radiation from the sun, and converts the heat and light from the sun into an “ideal” radiation, which illuminates the photovoltaic cell, enabling higher conversion efficiency. As a result, the device’s efficiency is increased from 30% (the conventional value for photovoltaic devices), to 50%.

The inspiration for the breakthrough comes from optical refrigeration, where the absorbed light is re-emitted at higher energy, thereby cooling the emitter. The researchers developed a technology that works similarly, but with sunlight.

“Solar radiation, on its way to the photovoltaic cells, hits a dedicated material that we developed for this purpose, the material is heated by the unused part of the spectrum,” says graduate student Assaf Manor, who led the study as part of his PhD work. “In addition, the solar radiation in the optimal spectrum is absorbed and re-emitted at a blue-shifted spectrum. This radiation is then harvested by the solar cell. This way both the heat and the light are converted to electricity.”

The group hopes to demonstrate a full operating device with record efficiency within 5 years’ time. If they are successful, they feel could become a disruptive technology in solar energy. ” Source: https://www.technion.ac.il/en/2016/11/photovoltaic-cells-70-efficiency/ Expected lead time: 5 years.

“Nature” science journal paper on the Technicon process: https://www.nature.com/articles/ncomms13167
“Thermally enhanced photoluminescence for heat harvesting in photovoltaics”
Assaf Manor, Nimrod Kruger, Tamilarasan Sabapathy & Carmel Rotschild

Article number: 13167 (2016)
doi:10.1038/ncomms13167 Received:
24 February 2016
Accepted:
08 September 2016
Published:
20 October 2016

“Abstract: The maximal Shockley–Queisser efficiency limit of 41% for single-junction photovoltaics is primarily caused by heat dissipation following energetic-photon absorption. Solar-thermophotovoltaics concepts attempt to harvest this heat loss, but the required high temperatures (T>2,000 K) hinder device realization. Conversely, we have recently demonstrated how thermally enhanced photoluminescence is an efficient optical heat-pump that operates in comparably low temperatures. Here we theoretically and experimentally demonstrate such a thermally enhanced photoluminescence based solar-energy converter. Here heat is harvested by a low bandgap photoluminescent absorber that emits thermally enhanced photoluminescence towards a higher bandgap photovoltaic cell, resulting in a maximum theoretical efficiency of 70% at a temperature of 1,140 K. We experimentally demonstrate the key feature of sub-bandgap photon thermal upconversion with an efficiency of 1.4% at only 600 K. Experiments on white light excitation of a tailored Cr:Nd:Yb glass absorber suggest that conversion efficiencies as high as 48% at 1,500 K are in reach.”Source: Ibid.

SSPS : Space Solar Power System, Japan

“J-spacesystems has been studying Space Solar Power System (SSPS) as an alternative future energy resource under a support of METI (The Ministry of Economy, Trade and Industry) and the other related agency for the past several years.

“The study has covered from basic laboratory testing level to the practical power plant level. The activities have been supported by working committee. Participants of the committee were selected from people of wide range of backgrounds. They are experts for respective technologies working for universities, industries and research organization.”

“The Working Committee has investigated a simple, technically feasible, and practical configuration SSPS which consists of a large power generation/transmission panel suspended by multi-tether wires from a bus system above the panel. The upper surface of the generation/transmission panel is covered with solar cells, and the lower surface mounts transmitting phased array antenna elements and solar cells. An artist concept of the tethered SSPS is shown in Fig.2.”

The attitude is automatically stabilized by the gravity gradient force in the tether configuration. So the antenna surface of the panel is always oriented towards the earth without any active attitude control. No moving structure in a large scale makes this system highly robust and stable. The power generation/transmission panel consists of identical modules, which greatly contributes to the low cost production, testing, and realizing high quality. Another innovative feature of the module is the application of wireless LAN system for the signal interface among those panels, which leads to the reliable deployment, integration, and maintenance.
Fig3 shows concept of the “Baseline type” SSPS which is capable of 1.6GW power supply maximum and 1GW average on the ground. It is composed of a power generation/transmission panel of 2.6×2.4 km suspended by multi-tethers deployed from a bus system which is located at 10 km upward. The panel consists of sub-panels of 100 mx100 m with 0.1m thickness. Each sub-panel consists of module panels 1 mx1 m size. There is no wired signal interface between module panels. The control signal and reference signal for each module panel are provided from the bus system by the wireless LAN.
The power generation of the baseline type SSPS varies with the local time as the sun angle changes as shown in Fig.4. The average power amounts to 64% of the maximum power.”

“In order to utilize wireless power transmission, we have to consider three main elements:

“First element is generation of RF energy from the electric power.
The second element is to send the energy to the point of interest.
The last element is the receiving RF energy and converting it to DC electric power.
In addition to these elements, we have to understand and control unwanted emission and reflection of RF energy. We have covered these elements in our testing in some extent.

“Beam Control Experiment
The beam control experiment was initiated from 2001. The active array panel with phase shifters, AIA#1, and the hardware retro-directive active integrated array panel, AIA#2, were developed and tested. The combination transmission test was also carried out.

The purpose of the development was to understand the issue derived by the microwave beam steering with integrated panels. And its evaluation was carried out in the anechoic chamber of METLAB, which is the microwave power transmission experiment facility of the Kyoto University. Fig 5 shows experiment in test facility.”

“In 2007, high accurate beam control experiment was carried out using the phased array antenna (5.8GHz, one-dimensional, 12 elements, about 40 cm wide).

Also, experiment of synchronized reference control system by closed loop technique for multiple phased array panels were carried out.”

source: http://www.jspacesystems.or.jp/en_project_ssps/

Japan Demoes Wireless Power Transmission for Space-Based Solar Farms
Sending kilowatts of power half a kilometer is just a start. Japan is planning orbiting solar farms in the 2030s
By Evan Ackerman

: Photo: Mitsubishi Heavy Industries
Phasers Locked on Target: In a test of space-based solar power, Mitsubishi Heavy Industries and JAXA sent 10 kilowatts 500 meters by microwave.

Some think the way to make solar power the backbone of a renewable energy economy is to avoid the problematic Earth entirely and head out into space, where the sun is always shining and weather means something entirely different. Solar power satellites (SPS) are more than a concept: it’s an area of active research and development, led by the Japan Aerospace Exploration Agency (JAXA). JAXA explained its 25 year technology development roadmap that culminates in a 1 gigawatt SPS sending solar power back to Earth in the 2030s in IEEE Spectrum last year. Last week, JAXA and Mitsubishi demonstrated their progress on one of the most difficult components of that system: long range wireless power transmission.

Space-based solar power on a commercially viable scale will be an enormous undertaking. For an output of 1 gigawatt, Japan is planning on deploying a solar collector weighing over 10,000 metric tons and measuring several kilometers across. It would live in geosynchronous orbit, some 36,000 kilometers from Earth.

Arguably, the most difficult part of this whole business (from a technological perspective) is getting the power from the satellite back down to Earth where we can actually use it, and until we can find a long enough extension cord, there’s only one way to make it work: wirelessly.

The only efficient ways to transmit power wirelessly over a very long distance, according to JAXA researchers, is with either lasers or microwaves. Lasers are impractical because they’d run into the same problems that solar power does on Earth: they don’t work through clouds. Microwaves, though, work even if the weather is bad, so they’re what JAXA has been planning on using to transmit power.

On Thursday, JAXA was able to deliver 1.8 kilowatts “with pinpoint accuracy” to a receiving antenna (rectenna) 55 meters away using carefully directed microwaves. According to JAXA, this is the first time that anyone’s been able to send such a high power output with this level of direction control. Also on Thursday, Mitsubishi (in partnership with JAXA) managed to send 10 kilowatts of power over a distance of 500 meters, using larger antennas with more of an emphasis on power over precision.

The obvious question here is one of efficiency: being able to transmit power is great, but if you lose most of it along the way, will the overall system ever reach commercial viability? At this point, the conversion system (solar to DC to microwave to DC to AC) is about 80 percent efficient, but that excludes loss of energy in transit. Neither JAXA nor Mitsubishi are commenting on the efficiency of these specific tests (which, to be fair, weren’t’t optimized for efficiency), but we do know that as of last year, JAXA expected a 1.6 kilowatt microwave beam to yield a rectenna output of about 350 watts from a 50 meter test.

Within the next five years or so, Mitsubishi is hoping that they’ll be able to use this system for short range high power delivery (like electric car charging), and medium range delivery of small amounts of power (like powering warning lights on transmission towers). Meanwhile, JAXA is planning on testing the technology in space by 2018, with a small satellite transmitting several kilowatts from low Earth orbit to a microwave receiver on the ground. JAXA hopes to have a 100 kW satellite in orbit by 2021, and a 200 MW version by 2028. By 2031, if everything goes well, a 1 gigawatt commercial pilot plant will be in operation, with a full on commercial space-based power industry to kick off with one launch per year starting in 2037.” end quote, source: IEEE Spectrum at https://spectrum.ieee.org/energywise/green-tech/solar/japan-demoes-wireless-power-transmission-for-spacebased-solar-farms

Nuclear industry, that icon of undelivered futuristic broken promises, will scoff at these ideas and anything else which might, in the PR battle, cause it to loose even more honest face.

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