Powered by the Sun: Boosting Solar Efficiency

solar1Improving the efficiency of solar power – which is currently the most promising alternative energy source – is central to ensuring that it an becomes economically viable replacement to fossil fuels, coal, and other “dirty” sources. And while many solutions have emerged in recent years that have led to improvements in solar panel efficiency, many developments are also aimed at the other end of things – i.e. improving the storage capacity of solar batteries.

In the former case, a group of scientists working with the University of Utah believe they’ve discovered a method of substantially boosting solar cell efficiencies. By adding a polychromat layer that separates and sorts incoming light, redirecting it to strike particular layers in a multijunction cell, they hope to create a commercial cell that can absorb more wavelengths of light, and therefor generate more energy for volume than conventional cells.

EMSpectrumTraditionally, solar cell technology has struggled to overcome a significant efficiency problem. The type of substrate used dictates how much energy can be absorbed from sunlight — but each type of substrate (silicon, gallium arsenide, indium gallium arsenide, and many others) corresponds to capturing a particular wavelength of energy. Cheap solar cells built on inexpensive silicon have a maximum theoretical efficiency of 34% and a practical (real-world) efficiency of around 22%.

At the other end of things, there are multijunction cells. These use multiple layers of substrates to capture a larger section of the sun’s spectrum and can reach up to 87% efficiency in theory – but are currently limited to 43% in practice. What’s more, these types of multijunction cells are extremely expensive and have intricate wiring and precise structures, all of which leads to increased production and installation costs.

SolarCellResearchIn contrast, the cell created by the University of Utah used two layers — indium gallium phosphide (for visible light) and gallium arsenide for infrared light. According to the research team, when their polychromat was added, the power efficiency increased by 16 percent. The team also ran simulations of a polychromat layer with up to eight different absorbtion layers and claim that it could potentially yield an efficiency increase of up to 50%.

However, there were some footnotes to their report which temper the good news. For one, the potential gain has not been tested yet, so any major increases in solar efficiency remain theoretical at this time. Second, the report states that the reported gain was a percentage of a percentage, meaning that if the original cell efficiency was 30%, then a gain of 16% percent means that the new efficiency is 34.8%. That’s still a huge gain for a polychromat layer that is easily produced, but not as impressive as it originally sounded.

PolyChromat-640x353However, given that the biggest barrier to multi-junction solar cell technology is manufacturing complexity and associated cost, anything that boosts cell efficiency on the front end without requiring any major changes to the manufacturing process is going to help with the long-term commercialization of the technology. Advances like this could help make technologies cost effective for personal deployment and allow them to scale in a similar fashion to cheaper devices.

In the latter case, where energy storage is concerned, a California-based startup called Enervault recently unveiled battery technology that could increase the amount of renewable energy utilities can use. The technology is based on inexpensive materials that researchers had largely given up on because batteries made from them didn’t last long enough to be practical. But the company says it has figured out how to make the batteries last for decades.

SONY DSCThe technology is being demonstrated in a large battery at a facility in the California desert near Modeso, 0ne that stores one megawatt-hour of electricity, enough to run 10,000 100-watt light bulbs for an hour. The company has been testing a similar, though much smaller, version of the technology for about two years with good results. It has also raised $30 million in funding, including a $5 million grant from the U.S. Department of Energy.

The technology is a type of flow battery, so called because the energy storage materials are in liquid form. They are stored in big tanks until they’re needed and then pumped through a relatively small device (called a stack) where they interact to generate electricity. Building bigger tanks is relatively cheap, so the more energy storage is needed, the better the economics become. That means the batteries are best suited for storing hours’ or days’ worth of electricity, and not delivering quick bursts.

solarpanelsThis is especially good news for solar and wind companies, which have remained plagued by problems of energy storage despite improvements in both yield and efficiency. Enervault says that when the batteries are produced commercially at even larger sizes, they will cost just a fifth as much as vanadium redox flow batteries, which have been demonstrated at large scales and are probably the type of flow battery closest to market right now.

And the idea is not reserved to just startups. Researchers at Harvard recently made a flow battery that could prove cheaper than Enervault’s, but the prototype is small and could take many years to turn into a marketable version. An MIT spinoff, Sun Catalytix, is also developing an advanced flow battery, but its prototype is also small. And other types of inexpensive, long-duration batteries are being developed, using materials such as molten metals.

Sumitomo-redox-flow-battery-YokohamaOne significant drawback to the technology is that it’s less than 70 percent efficient, which falls short of the 90 percent efficiency of many batteries. The company says the economics still work out, but such a wasteful battery might not be ideal for large-scale renewable energy. More solar panels would have to be installed to make up for the waste. What’s more, the market for batteries designed to store hours of electricity is still uncertain.

A combination of advanced weather forecasts, responsive fossil-fuel power plants, better transmission networks, and smart controls for wind and solar power could delay the need for them. California is requiring its utilities to invest in energy storage but hasn’t specified what kind, and it’s not clear what types of batteries will prove most valuable in the near term, slow-charging ones like Enervault’s or those that deliver quicker bursts of power to make up for short-term variations in energy supply.

Tesla Motors, one company developing the latter type, hopes to make them affordable by producing them at a huge factory. And developments and new materials are being considered all time (i.e. graphene) that are improving both the efficiency and storage capacity of batteries. And with solar panels and wind becoming increasingly cost-effective, the likelihood of storage methods catching up is all but inevitable.

Sources: extremetech.com, technologyreview.com

 

Powered by the Sun: Bringing Solar to the Developing World

Magnificent CME Erupts on the Sun - August 31All over the world, the goal of bringing development to impoverished communities and nations – but in ways that won’t cause additional harm to the natural environment – remains problematic. As the cases of China and India demonstrate, the world’s fastest growing economies in the 21st century, rapid industrialization may bring economic development, but it comes with a slew of consequences.

These include urban sprawl, more emissions from cars and public transit, and the poisoning of waterways through toxic runoff, chemicals and fertilizers. With seven billion people living in the world today, the majority of which live in major cities and are dependent on fossil fuels, it is important to find ways to encourage growth that won’t make a bad situation worse.

solar_quetsolBut to paraphrase an old saying, crisis is the mother of creative solutions. And amongst forward-looking economist and developers, a possible solution is take the latest advancements in solar, wind, tidal power and biofuels, and tailor them to meet the needs of local communities. In so doing, it is hoped that the developing world could skip over the industrial phase, reaping the benefits of modernization without all the dirty, unhealthy consequences.

Two such men are Juan Rodriguez – a young man who was studying for his business administration at the Universidad Francisco Marroquin in and cut his teeth working for major multinationals like Pampers, Pepto Bismol and Pantene – and his childhood friend Manuel Aguilar, a Harvard graduate with a degree in astrophysics who had gone on to manage a global hedge fund.

solar_quetsol1Three years ago, the two agreed that they were looking for something else and began investigating renewable energy. The result was Quetsol, a company that uses solar energy to improve the quality of life of poor communities living off the electrical grid. In Rodriguez’s and Aguilar’s native Guatemala, such poverty is widespread, with close to 20% of the population living without electricity and relying primarily on candles for light.

This picture of poverty is not exactly news. But after spending a year visiting close to 100 such communities, Rodriguez and Aguilar began to get a clear picture of why solar hadn’t yet succeeded. As Rodriguez put it:

Going to a community and talking about solar power isn’t like going into a community and talking about space travel. It is something that people have already seen, because NGOs have donated solar systems to these communities for decades. In many cases, the systems worked perfectly, but eventually the batteries died, and nobody was there to service them.

solar_quetsol2There solution was to start from the bottom up, using the free-market principle of adapting their approach to meet local needs. This would involve identifying communities before visiting them, taking into account how many people were living without electricity, and what the housing situation was like. When they then visited these communities, they sought out community leaders and held public meetings to learn about them and present their ideas.

Buildings relationships with local communities was a challenge, but so was creating a product for a market whose needs ranged from basic lighting and cell phone charging to powering a refrigerator all day. What they found was that unelectrified communities were relying on terribly inefficient means, ranging from diesel generators to walking to the nearest electrified community to plug in a phone.

solar_quetsol3What was resulted was a Solar Kit, consisting of a 10W Solar Panel, a control box with 7 Amp Battery, 2  LED Bulbs  (and a third optional bulb), and a universal cell phone charger. This kit has the ability to provide five hours of electricity to a house made up of two rooms that measure roughly 25 square meters (225 square feet) each. This is the typical design of homes in rural Guatemala, with one room serving as the bedroom and the other as the kitchen.

With that done, they began working on their sales strategy. Initially, this consisted of working with microfinance credit institutions to help families and communities purchase their solar kits. But after watching too many credit applications get rejected, they took a page from the telecom companies that have made cell phones ubiquitous in Guatemala, Basically, they switched to a pay-as-you-go plan.

solar_quetsol4Today, Quetsol employs a staff of 20 people and boasts board members like Google’s Tom Chi. There product line has also expanded, with the Q1 Solar Kit being supplemented by the Q3, a heavier model that boasts a 75W solar panel, an 85 Amp Battery, and five LED bulbs. The Q2 Kit – a middle of the road model with a 30W panel, 34 amp battery and 3 bulbs – is soon to be released.

But most importantly of all, they have electrified more than 3,500 homes in Guatemala thus far. But that is just a drop in the bucket compared to their long-term goal. Basically, the organization is viewing Guatemala as a stepping stone to all of Latin America as well as Africa by 2015. By 2016, they’d like to tackle the nearly 700 million off-the-grid homes in Asia.

Might sound ambitious, but Rodriguez and Marroquin feel they have the business acumen and social entrepreneurial savvy to pull it off. And given their background and business model, I’d say they are about right. Combined with other technologies that merge local needs with clean, efficient, and renewable means, development in the developing world might actually be an eco-friendly possibility.

Sources: fastcoexist.com, quetsol.com