By Dave Elliott
A new book ‘The Switch’ (Profile Books) by Chris Goodall suggests that the combination of cheap solar photovoltaics and cheap batteries will be a global winner. It is certainly true that the cost of PV solar has been falling rapidly, outstripping predictions, and even confounding most of the PV optimists, as the technology has improved and markets for it have built. Goodall sees this as a continuing process, at maybe up to a 40% annual growth rate, with PV soon becoming the dominant energy source globally, a view that he notes even some conservative oil companies now share. Lithium ion battery costs have also fallen significantly. So, with wind also providing inputs when there is no sun, we are all set! A similar line was taken in Tony Seba’s book ‘Clean Disruption of Energy and Transportation’. PV and batteries are going to boom worldwide, and electric vehicles too.
By Dave Elliott
Some say that the vision of households and businesses moving largely off-grid by storing solar power generated during the day for use overnight is close to becoming a reality. The prospects for moving entirely off grid may be limited – most projects will still need grid links to allow for top-ups when solar input is low for long periods and the stores are exhausted. However, that still leaves a significant potential for self-generation and storage. (more…)
By Dave Elliott
PV solar continues its spectacular price reduction and that’s led to large-scale deployment, as in Germany, which now has around 36GW in place, and globally, with around 180 GW. PV was initially expensive, but prices are now much lower, thanks in part to Feed In Tariff systems around the EU, as under the EEG law in Germany, which has helped create a large market. With FiT levels now cut, will it continue to expand?
By Dave Elliott
The vehicle to grid (V2G) debate continues, offering a way to balance variable renewables and also demand peaks, by using the batteries of electric vehicles, linked to the grid when parked at home, to store excess power during low demand periods, ready to export when demand is high and renewables low. It sounds a clever idea but in addition to economic issues (e.g. the extra costs of the home-based power uploading system) it opens up some interesting logistical issues. (more…)
by Dave Elliott
In its business leader column on August 25th The Observer, said “If there is a body of opinion that states that wind farms and energy efficiency can fill the looming energy gap, then it is small and deeply unrepresentative”. www.theguardian.com/business/2013/aug/25/anger-fracking-cant-manage-without-gas
Germany is aiming to get at least 80% of its electricity from renewables by 2050, with overall energy demand cut by 50%, so the Observer seems to have it wildly wrong, certainly long term. And in fact, far from being marginal, around 50 countries are already getting more than 60% of their electricity from renewables in the form of hydro, some of them near 100%. http://k.lenz.name/LB/?p=6525. Longer term, dozens of studies claim that renewables could supply 100% of the worlds electricity in many countries by around 2050. http://www.mng.org.uk/gh/scenarios.htm. That is what Denmark and New Zealand are aiming for and many others see renewable as their main future energy option- with China leading the way.
by Dave Elliott
In my last post I looked at various types of photovoltaic and photoelectric cell, which convert light in electricity. In most cases cell efficiency falls with increased temperature, but in this post I look at devices that operate on heat and on the infra -red (IR) part of the light spectrum. There are some hybrid solar thermal/PV systems, with, for example, a semi-transparent PV sheet on top of a heat absorbing solar collector. This ‘PV/T’ approach can not only keep the PV system cool, but also doubles up on land, roof (or wall) space usage. One such system, a PV array integrated with a SolarWall air-heating unit, was installed on a roof in the 2008 Beijing Olympic Village.
by Dave Elliott
Photovoltaic (PV) solar is moving ahead rapidly, with over 100GW now installed around the world at various scales. The attractions of PV are that it is a silent operating, relatively robust and an easy to fit technology, with no moving parts or plumbing requirements. But since PV cells use specially fabricated materials they were initially expensive. However that changed as volume production increased and technology improved. Indeed PV has one of the best unit cost/installed capacity ‘learning curve’ slopes in the renewable energy field. Progress down this curve seems likely to continue given that there are many new cell technologies emerging. They will increase energy conversion efficiency and reduce unit cost, since with higher efficiencies less cell material is needed. Depending on the type, commercial silicon cells can have energy conversion efficiencies of 10-18%. More advanced cells, using more exotic materials, can achieve more, at least under laboratory condition e.g., the US National Renewable Energy Labs say copper indium gallium selenide (‘CIGS’) solar cells can be almost 20% efficient.
Solar energy has been the focus of research effort for decades now, and some interesting new technologies have emerged. Most of the effort has been going into improving cell efficiency, using new materials or configurations, but there have also been some novel developments based on completely new concepts. For example, as reported in New Scientist last year (20/12/10), the US Dept of Energy’s Idaho National Lab has developed a device that works on infra-red radiation – which accounts for about half of the available energy in the solar spectrum. Moreover IR is re-emitted by the Earth’s surface after the sun has gone down, so the device can capture some energy at night. Lab tests have suggested that a complete system could have an overall efficiency of 46%; much higher than the best silicon cell at 25%. And they would not be so directionally sensitive. The new device doesn’t rely on photons liberating electrons in semi conductors, as in conventional solar cells. Instead it uses tiny nano-scale antennas which resonate when hit by light waves, generating an alternating current at very high frequency. That has to be rectified to be useful- tricky it seems at nano-scale.
There are also some other clever new technologies on the horizon. For example A US team led by a North Carolina State University researcher have developed solar cell with a water-based gel infused with light-sensitive molecules – the researchers used plant chlorophyll in one of the experiments and have shown that water-gel-based solar devices can produce electricity.
The researchers say “We do not want to over-promise at this stage, as the devices are still of relatively low efficiency and there is a long way to go before this can become a practical technology. However, we believe that the concept of biologically inspired ‘soft’ devices for generating electricity may in the future provide an alternative for the present-day solid-state technologies.”
Just as intriguing, New Energy Technologies Inc. has developed a room temp ‘spray-on’ solar PV coating for glass windows, using nano-particles 4 times smaller than a grain of rice . It’s claimed to cut solar cost/kW by a third and leaves windows translucent. www.newenergytechnologiesinc.com
Meanwhile, MIT has developed transparent organic PV cells, which can be used in windows. They only use near infra red wavelengths- the rest passes through: http://apl.aip.org/resource/1/applab/v98/i11/p113305_s1?bypassSSO=
Even more exotic, and moving beyond PV electricity production, is the prototype solar device that has been developed by researchers at CALTEC and in Switzerland which uses a quartz window and cavity to concentrate sunlight into a cylinder lined with cerium oxide, also known as ceria, which exhales oxygen as it heats up and inhales it as it cools. If, as in the prototype, hydrogen and/or water are pumped into the vessel, the ceria will rapidly strip the oxygen from them as it cools, creating hydrogen and/or carbon monoxide. The hydrogen produced could be used to fuel hydrogen fuel cells, while a combination of hydrogen and carbon monoxide can be used to create “syngas” for fuel.
The BBC web site reported that ‘the prototype is grossly inefficient, the fuel created harnessing only between 0.7% and 0.8% of the solar energy taken into the vessel. Most of the energy is lost through heat loss through the reactor’s wall or through the re-radiation of sunlight back through the device’s aperture. But the researchers are confident that efficiency rates of up to 19% can be achieved through better insulation and smaller apertures. Such efficiency rates, they say, could make for a viable commercial device’.
However, in terms of even more radical large-scale developmental concepts, University of Tokyo researchers have launched a Sahara Solar Breeder project, aiming to use desert sand to produce PV solar units and desert sun to ultimately generate 50% of the planet’s electricity, by distributing solar energy globally through a superconducting supergrid.
As I mentioned in my previous Blog, the idea is that power generated by the first wave of plants would be used to “breed” more silicon manufacturing and solar energy plants, which would in turn be used to breed yet more in a “self-replicating” system.
The initiative is funded by Japan’s Ministry of Education, Culture, Sports, Science and Technology (JST) and the Japan International Cooperation Agency (JICA) under the auspices of the International Research Project on Global Issues, which will fund the project to the tune of 100 million Yen ($1.2 million USD) annually for five years.
The aim of this initial five-year phase will be to demonstrate the possibility of manufacturing high quality silicon from desert sand and of building a high-temperature superconducting long-distance DC power supply system. But they suggest that it should be possible to generate 50% of global electricity globally with solar by 2050 .
Clearly many of these ideas will take some time to develop to be viable options, and some won’t succeed. But the pace of change in the solar world is quite dramatic. There is already over 40GW (peak) of conventional PV capacity in place globally and rapid growth continues, with new technologies and applications feeding in. For example over 20 MW of large-scale concentrator photovoltaics (CPV) systems are now connected to the grid, and CPV should reach GW level in the next 5 years, according to the European Photovoltaic Industry Association. Module efficiency in current power plants has reached 25-27% and is expected to grow to 30% by 2012. One of the attractions of CPV is the simple fact that, at present, mirrors, for focussing sunlight, are less expensive than PV cells.
New cheaper, light weight scratch resistant mirror materials are also emerging for use with concentrating solar (thermal) power (CSP) systems: www.mulkre.com That could make CPV, as well as CSP, more competitive. But even without that, focussed solar heat CSP seems to be booming. Some are hybrid systems with gas fired back-up/parallel generation, but with molten salt heat stores being added to some projects to allow for continued solar generation overnight.
Currently there is around 3 MW of CSP capacity in place globally and over 50 MW of new large-scale projects is being deployed around the world, mainly in Spain and the USA, but also in N Africa and the Middle East (see my last Blog). However, some say CPV will overtake CSP. Either way solar electricity generation looks likely to prosper, with much talk of price parity with conventional power sources within the next few years.
*For an interesting series of youtube videos on the many solar innovation projects in the USA, many of them seeking to copy/adapt phototsynthsis, see: http://www.energyfrontier.us/videos