Posts Tagged‘solar’

Polymer Photovoltaic Cells See Efficiency Boost with Better Designs.

The solar cells you see on many roofs today are built out of silicon, the same stuff that powers your computer and smartphone. The reasons for this are many but it mostly comes down to silicon’s durability, semiconductor properties and ease at which we can mass produce them thanks to our investments in semiconductor manufacturing. However they’re not the only type of solar cell we can create, indeed there’s a different type that’s based on polymers (essentially plastic) that has the potential to be much cheaper to manufacture. However the technology is still very much in its infancy with the peak efficiency (the rate at which it can convert sunlight into electricity) being around 10%, far below even that available from commercial grade panels. New research however could change that dramatically.

88339d8cc8_polymere_fullerene

The current standard for organic polymer based solar cells utilizes two primary materials. The first is, predictably, an organic polymer that can accept photons and turn them into electronics. These polymers are then doped with a special structure of carbon called fullerene, more commonly known as buckyballs (which derive their name from their soccer ball like structure). However the structures that form with current manufacturing processes are somewhat random. This often means that when a photon produces a free electron it recombines before it can be used to generate electricity which is what leads to polymer cell’s woeful efficiency. New research however points to a way to give order to this chaos and, in the process, greatly improve the efficiency.

Researchers at the USA’s Department of Energy’s SLAC National Accelerator Laboratory have developed a method to precisely control the layout of the polymers and fullerene, rather than the jumbled mess that is currently standard. They then used this method to test various different arrangements to see which one produced the highest efficiency. Interestingly the best arrangement was one that mimicked the structure we see in plants when they photosynthesize. This meant that the charge created in the polymer by a photon wasn’t recombined instantly like it usually was and indeed the polymers were able to hold charge for weeks, providing a major step up in efficiency.

Whilst this research will go a long way to solving one of the major problems with polymer based solar cells there are still other issues that will need to be addressed before they become commercially viable. Whilst a typical silicon solar cell will last 20 years or more a polymer one will only last a fraction of that time, usually only 4 years or so with current technology. For most solar cells that amount of time is when they’ve just paid back their initial investments (both in terms of energy and revenue) so until they get past this roadblock they will remain an inferior product.

Still research like this shows there’s potential for other technologies to compete in the same space as silicon, even if there are still drawbacks to be overcome. Hopefully this research will provide further insights into increasing the longevity of these panels at the same time as increasing their efficiency. Then polymer panels could potentially become the low cost, mass produced option enabling a new wave of investment to come from consumers who were previously locked out by current photovoltaic pricing.

Tesla’s Powerwall: Home Power Revolutionized.

The problem that most renewables face is that they don’t generate power constantly, requiring some kind of energy storage medium to provide power when its not generating. Batteries are the first thing that comes to everyone’s mind when looking for such a device however the ones used for most home power applications aren’t anymore advanced than your typical car battery. Other methods of storing power, like pumped hydro or compressed air, are woefully inefficient shedding much of the generated power away in waste heat or in the  process of converting it back to electricity when its needed. Many have tried to revolutionize this industry but few have made meaningful progress, that was until Tesla announced the Powerwall.

Tesla Powerwall

The Powerwall is an interesting device, essentially a 7KW (or 10KW, depending on your application) battery that mounts to your wall that can provide power to your house. Unlike traditional systems which were required to be constructed outside, due to the batteries producing hydrogen gas, the Powerwall can be mounted anywhere on your house. In a grid-connected scenario the Powerwall can store power during off-peak times and then release it during peak usage thereby reducing the cost of your energy consumption. The ideal scenario for it however is to be connected to a solar array on the roof, storing that energy for use later. All of this comes at the incredibly low price point of $3,000 for the 7KW model with the larger variant a mere $500 more. Suffice to say this product has the potential for some really revolutionary applications, not least of which is reducing our reliance on fossil fuel generated power.

The solar incentives that many countries have brought in over the last few years has seen an explosion in the number of houses with domestic solar arrays. This, in turn, has brought down the cost of getting solar installed to ridiculously low levels, even less than $1/watt installed in some cases. However with the end of the feed-in tariffs these panels are usually not economical with the feed-in rates usually below that of the retail rate. Using a Tesla Powerwall however would mean that this energy, which would otherwise be sold at a comparative loss, could be used when its needed. This would reduce the load on the grid whilst also improve the ROI of the panels and the Powerwall system, a win-win in anyone’s books.

It would be one thing if Tesla was just making another product however it seems that Elon Musk has a vision that extends far beyond just ripping the battery out of its cars and selling them as grid connected devices. The keynote speech he gave a few days ago is evidence of that and is worth the watch if you have the time:

In its current incarnation the Tesla Powerwall is a great device, one that will make energy storage feasible to a much wider consumer base. However I can’t help but feel that this is just Tesla’s beachhead into a much larger vision and that future revisions of the Powerwall product will likely bring even larger capacities for similar or lower prices. Indeed this is all coming to us before Tesla has completed their Gigafactory-1 which is predicted to reduce the cost of the batteries by some 30% with further iterations driving it down even more. Suffice to say I’m excited about this as it makes a fully renewable future not only inevitable, but tantalizingly close to reality.

Are Solar Freakin’ Roadways Feasible?

The main substrate of our roads hasn’t changed much in the past 50 years. Most of our roads these days are asphalt concrete with some being plain old concrete with a coarse aggregate in them. For what we use them for this isn’t really an issue as the most modern cars can still perform just as well on all kinds of roads so the impetus to improve them is low. There have been numerous ideas put forth to take advantage of the huge swaths of road we’ve laid down over the years, many seeking to use the heat they absorb to do something useful. One idea though would be a radical departure from the way we currently construct roads and it could prove to be a great source of renewable energy.

Solar Roadways

Solar (Freakin’) Roadways are solar tiles that can be laid down in place of regular road. Their surface is tempered glass that’s durable enough for a tractor to trundle over it and provides the same amount of grip that a traditional asphalt surface does. Underneath that surface is a bunch of solar panels that will generate electricity during the day. The hexagonal panels also include an array of LEDs which can then be used to generate lane markers, traffic signs or even alert drivers to hazards that have been detected up the road. Both the concept art and the current prototypes they have developed look extremely cool and with their Indiegogo campaign already being fully funded it’s almost a sure bet that we’ll see roads paved with these in the future.

The first question that comes to everyone’s mind though is just how much will roads paved in this way cost, and how does that compare to traditional roads?

As it turns out finding solid numbers on the cost of road construction per kilometer is a little difficult as the numbers seem to differ wildly depending on who you ask. A study that took data from several countries states that the median cost is somewhere around $960,000/km (I assume that’s USD) whereas councils from Australia have prices ranging from $600,000/km to $1,159,000/km. Indeed depending on how complicated the road is the costs can escalate quickly with Melbourne’s Eastlink road costing somewhere on the order of $34,000,000 per kilometer laid down. In terms of feasibility for Solar Roadways I’d say that they could be competitive with traditional roads if they could get their costs to around $1,000,000/km at scale production something which, in my mind, seems achievable.

Unfortunately Solar Roadways isn’t forthcoming with costs as of yet mostly due to them being in the prototype stage. Taking a look over the various components they list though I believe the majority of the construction cost will come from the channels beneath the panels as bulk prices for things like solar panels, tempered glass and PCBs are quite low. Digging and concreting the channels required to carry the power infrastructure could easily end up costing as much as a traditional road does so potentially we’re looking at a slightly higher cost per km than our current roads. Of course I could be horribly wrong about this since I’m no civil engineer.

The cost would be somewhat offset by the power that the solar roads would generate although the payback period is likely to be quite long. Their current prototypes are 36 watt panels which they claim will go up to 52 watt for the final production module. I can’t find any measurements for their panels so I’ve eyeballed that they’re roughly 30cm per side giving them a size of about 0.2 square meters. This means that a square meter of these things could generate roughly 250 watts at peak efficiency. The output will vary considerably throughout the year but say you get 7 hours per day at 50% max output you’re looking at about 875 watts generated per square meter. Your average road is about 3 meters wide giving us 3000 square meters of generation area generating about 2,600kwh per day. The current feed in tariffs in Australia would have 1km of Solar Roadways road making about $1000 / day giving a pay off time of around 3 years. My numbers are likely horribly skewed to be larger than they’d be realistically though (there are many more factors that come into play) but even slashing the efficiency down to 10% still gives you a pay back time of 15 years, longer than the current expected life of the panels.

As an armchair observer then it does seem like Solar Roadways’ idea is feasible and could end up being a net revenue generator for those who choose to adopt it. All of my numbers are based on my speculation though so there are numerous things that could put the kibosh on it but it’s at least taking to the real world implementation stage to see how things pan out. Indeed should this work as advertised then the future of transportation could be radically different, maybe enough to curb our impact on the global ecosystem. I’m looking forward to see more from Solar Roadways as a future with them looks to be incredibly exciting.

Luna Ring Could Bring Terawatts of Energy to Earth.

Do you remember the Microwave Power Plant in Sim City 2000? The idea behind them was an intriguing one, you launched a satellite into orbit with a massive solar array attached and then beamed the power back down to Earth using microwaves that were collected at a giant receiver. Whilst it worked great most of the time there was always the risk that the beam would stray from its target and begin setting fire to your town indiscriminately, something which the then 11 year old me thought was particularly hilarious. Whilst we’ve yet to see that idea (or the disasters that came along with it, but more on that in a moment) the idea of putting massive solar arrays in orbit, or on a nearby heavenly body, are attractive enough to have warranted significant study.

Shimizu Master Plan Luna RingThe one limiting factor of most satellite based designs though is that they can’t produce power constantly due to them getting occluded for almost half their orbital period by Earth. Shimizu Corporation’s idea solves this issue in the most fantastical way possible: by wrapping our moon in a wide band of solar panels, enabling it to generate power constantly and beam it back down to Earth. Such an endeavour would seem like so much vapourware coming from anyone else but Shimizu is one of Japan’s leading architectural and engineering firms with annual sales of $14 billion. If there’s anyone who could make this happen it’s them and it aligns with some of the more aggressive goals for space that the Japanese government has heavily invested in of late.

The idea is actually quite similar to that of its incarnation in Sim City. Since the Moon is tidally locked with Earth (I.E. one side of the moon always points towards us) there only needs to be a single base station on the moon. Then a ring of solar panels would then be constructed all the way around the Moon, ensuring that no matter what the position of Moon, Earth and the Sun there will always be an illuminated section. There would have to be multiple base stations on Earth to receive the constantly transmitted power but since the power beams would be pointable they needn’t be placed in any particular location.

Of course such an idea begs the question as to what would happen should the beam be misaligned or temporarily swing out of alignment, potentially roasting anything in the nearby vicinity. For microwaves this isn’t much of a threat since the amount of power delivered per square meter is relatively low with a concentrated burst of 2 seconds barely enough to raise your body temperature by a couple degrees. A deliberately mistargeted beam could do some damage if left unchecked but you could also combat it very easily by just putting up reflectors or the rectilinear antennas to absorb it. The laser beams on the other hand are designed to be “high density” so you’d want some rigorous safety systems in place to make sure they didn’t stray far from the course.

Undertaking such a feat would require several leaps in technology, not least of which would be in the automation of its construction, but it’s all based on sound scientific principles. It’s unlikely that we’ll even see the beginnings of something like this within the next couple decades but as our demand for power grows options like this start to look a lot more viable. I hope Shimizu pursues the idea further as they definitely have the resources and know how to make it happen, it’s all a question of desire and commitment to the idea.

 

Power in Space.

One thing that’s always a big issue for any project in space is how you’re going to power whatever you’re sending up there. As it turns out the methods that we use to generate power up in space are extremely varied and in fact many of them paved the way for technologies we now use back here on earth. However there are still some advances to be made and if we are to return to the moon and beyond there will have to be a breaking down of some old barriers in order to enable us to go further into space.

Many of the initial space craft that were sent up just had your traditional chemical batteries in them. For the most part these worked well, and since they had been around for such a long time they were a proven technology (something that is critical in any space endeavour). As time went on and missions became much more ambitious NASA moved from batteries to fuel cells and were the first to fly these in a space craft on their Gemini missions. Fuel cells are advantageous because not only do they produce power, but typically a decent amount of heat and water as well. In fact they are still used to power the space shuttle and will typically produce around 500 litres of water on whilst in space. This is invaluable as that’s 500Kg less water they have to bring with them and 500Kg more they can take into orbit.

Satellites are another matter entirely. Since they don’t need any of those bothersome human things like water and heat fuel cells aren’t the right choice for them and the majority of artificial satellites in orbit around earth and our nearby neighbours use good old fashioned solar power. At the distance we are from the sun the available power is somewhere in the order of 1400W/m² but that drops off dramatically as we reach further out into the solar system. In fact the amount of power available past mars is so little compared to where we are that there is only one mission currently scheduled to Jupiter that uses solar panels called Juno.

So what do we use when we want to explore the deep reaches of space? The current technology used in most missions is called a Radioisotope Thermoelectric Generator (RTG) which in essence uses heat from decaying radioactive material to provide heat and electricity. In the past they’ve coped a lot of flack for using these as environmental groups lament the potential for damaging the environment and spreading nuclear material across the earth. NASA has done extensive research on the matter but still runs up against endless red tape whenever they try to use one. The usefulness of these devices really can’t be overstated as they’ve given us such missions such as Voyager 1, which has been going strong for over 30 years and is slated to last for at least another 15. This kind of technology is going to form the basis of any mission that attempts to leave our solar system.

NASA has begun to make inroads into producing small nuclear reactors that would be used to power a moon base. For any kind of long duration time in space us humans need quite a lot more power than our robotic counterparts and we won’t be able to use RTGs to satisfy this requirement. Whilst I do understand some of the environmental concerns if I was going to trust anyone sending nuclear material into space it would be NASA, as they have a long track record of getting hazardous materials out of our atmosphere without incident. Unfortunately the environmentalists haven’t seen it that way, and continually put up roadblocks which inhibit progress.

Eventually though I’m sure we will be able to power our space based devices using nuclear power without the worry and red tape that we have now. As time goes by NASA and other space agencies will prove that the technology is sound after repeated launches and the controversy will be nothing but a memory. It is then we can start to look further out into our solar system, and hopefully, beyond.

Renewable Energy.

After my last foray into the controversial world of the environment and power generation (which generated some stimulating discussion and research for me) I thought it best to take a look at the renewable means of power generation and which of them have a future. I’ve had a bit of experience with most of the technology in the past with a few of my off site engineering lectures, a requirement for any engineering degree, being held on renewable energy technologies. My father also teaches renewable energy classes at the local TAFE here in Canberra, and I’ve seen quite a few interesting projects he’s been involved with over the years.

When we talk about renewable energy sources we’re looking for something that doesn’t rely on fossil fuels. The main candidates for renewable energy are:

Now not one of these solutions can provide meet all of the energy needs of the entire world and there’s many different factors to consider. The ideal solution will probably end up with a combination of many of these technologies (and some of the ones that are currently under development) just like the power generation we use today.

First the main consideration is base load power generation. Whilst this is usually trotted out as the argument to destroy the idea of using any form of renewable energy it does have raise a key points that need to be addressed. Many of the renewable energies I’ve mentioned (in fact just over half of them) can’t produce stable amounts of power. Solar, wind and oceanic technologies vary their power output significantly depending on their environment. To solve this issue base load generating stations like geothermal and biomass have to be used to supply that base level of power. The other alternative is to invest some storage technologies, like molten salt for solar thermal. For Australia I believe that geothermal and solar thermal are probably the way to go. This is because we have so much uninhabitable land that is very dry and sunny, something that these technologies thrive on. Photovoltaics are nice for smaller installations however they currently do not scale as well as the others, although that might all change when sliver cells take off¹.

Secondly load following plants are also required in order to accommodate variations in power requirements. Biomass and Hydroelectric are both options for this however I’m not entirely sure how well they can scale up. It may be more efficient to have more base load plants and just disconnect them from the grid. Whilst that may sound counter-intuitive it would be perfectly acceptable since the energy is usually not being harnessed anyway.

The last problem I’ve seen with the implementation of renewables is the lack of ideal locations for certain technologies. Geothermal requires geysers to be present or implementation of a hot rocks plant. Wind requires either high altitude or favourable wind environments such as offshore. Solar and solar thermal require a decent amount of sun and a nice flat area. You can see where I’m going with this, there’s a fair amount of work to be done to get these things in and working.

Having said all this, I’m still all for these technologies. All of the problems I’ve put forward are nothing short of solvable and eventually we’ll be forced into implementing these solutions. The great news is a lot of the supposedly big bag oil companies are in fact on board and supporting this kind of technology. The ones who aren’t will eventually fall by the wayside and we can only hope they come around before they pull an Enron and dissolve the company.

I still believe nuclear would be a great transition technology, but only time will tell.

¹I actually had the pleasure of meeting the developer of sliver technology, Andrew Blakers, back when I was a fledgling engineer. His technology does have the potential to change photovoltaics in a way that would make them highly viable. Origin Energy has some great pictures of the cells in development, and hopefully they’ll be commercially available soon.