ARPA-E Funding Personal Climate Control Systems with Robots, Foot Coolers, and More

Why heat or cool a whole building when you could heat or cool individual people instead?

7 min read

ARPA-E Funding Personal Climate Control Systems with Robots, Foot Coolers, and More
Photo: Evan Ackerman/IEEE Spectrum

ARPA-E is the Advanced Research Projects Agency-Energy, a DARPA-type government agency that funds energy-related high-risk, high-reward projects. Like most government agencies, they tend to bury their projects in strained, dull-sounding acronyms like DELTA, which stands for Delivering Efficient Local Thermal Amenities. But ARPA-E's DELTA project is, fortunately, much more interesting than it sounds: DELTA is funding a bunch of different ways in which climate control can be moved from building-level to personal level.

The problem that ARPA-E wants to solve with DELTA is the ridiculous amount of energy that we waste heating and cooling buildings that are, statistically speaking, almost entirely unoccupied. When you turn on the heat or the AC, you're dumping energy into changing the temperature of an entire structure, when all you really care about is the little area of comfort surrounding you. And if some people like it warmer and some people like it colder, one of those two groups is doomed to misery. It's a terrible, ridiculous system.

A much better approach would be to develop technologies for highly localized and customizable temperature control. Why bother heating or cooling an entire building, when all of the people inside it can instead customize their own little climate bubble to their ideal temperature? This is what ARPA-E's DELTA project is all about. Here’s a look at three different technologies from ARPA-E's annual summit that are in the process of moving from prototype to commercial reality within the next two years.

University of Maryland: RoCo, the Robotic Personal Conditioning Device

RoCo is a "roving comforter" robot. It's a heater and air conditioner on top of a mobile base that can lock onto your phone and autonomously follow you around, gently blowing warm or cold air at you to keep you at a comfortable temperature. Intelligent nozzles will direct air at the parts of your body that are most sensitive to thermal changes.

imgPhoto: Evan Ackerman/IEEE Spectrum

The robot is a prototype right now, as you can probably tell from the pics. But the core of the system, and the most difficult part, is functional: the air conditioner. Portable indoor air conditioners tend to be horribly inefficient, because there's nowhere to put the excess heat. Usually, you have to run a hose from the unit to the nearest window, and the air conditioner will blow hot air through that, but then you've essentially got the hose acting as a radiator, fighting against all of the work that the air conditioner is trying to do.

RoCo solves this problem with big canisters of paraffin wax, which it uses as a phase-change material heat dump. The wax absorbs excess heat from the air conditioner and melts, keeping all of that heat contained. Then, you let the robot sit somewhere overnight, and it will radiate the trapped heat to resolidify the wax, "recharging" itself to be ready for operation the following day.

The prototype can blow cold air at you for about two hours before all of its wax melts, but the researchers are looking at modifying the phase-change material with graphite to improve its heat-retention capacity. They're also thinking about what they might be able to do with all of that stored heat: for example, it could potentially be harvested to help charge your cell phone, or even used to help power the robot itself.

What's most impressive about RoCo is that the target price is just sixty bucks. Sixty. Personally, to a guy who writes about robots a lot, this seems unachievably optimistic. Even the researchers admitted to us that it's "a huge challenge." It may end up that you'll pay a bit more for the fully kitted-out mobile robot version, and the base rate will get you a robot that instead sits on the floor or on your desk. One other option is to replace the air conditioning hardware with a fan and the phase-change material with a bucket that you fill with ice. It wouldn't be as efficient, but it would work well, and be way, way cheaper.

If you were to use RoCo in your house instead of running your heat or AC, your energy consumption would decrease by a factor of seven. In a commercial building, you could save up to 30% on energy costs by allowing the temperature to rise or fall a bit above comfort levels, and using RoCos to make up the different on an individual basis. And of course, the robots could adjust their climate to the preferences of each person, but that's just a fringe benefit.

UMD researchers see RoCo being most immediately valuable in places like data centers or automated factories, where the only reason to keep them cool is because humans have to go in from time to time to do maintenance. If you had a personal cooling robot to follow you, though, you could be much more flexible with cooling.

By April, the first two RoCo prototypes will be functionally complete, with commercialization targeted for 2018 through a partnership with GE.

University of California, Berkeley: The Wirelessly-powered Office Chair that Heats and Cools Your Body

UMD's RoCo is an awesome idea, but since it's heating and cooling the area all around your body, it may not be the most efficient solution. UC Berkeley is focusing on heating only your body, by providing temperature control through a wirelessly-powered office chair.

imgPhoto: Evan Ackerman/IEEE Spectrum

The chair has both heating elements and small fans built into the back and seat, along with some insulation, a battery, and a small control panel that lets you adjust the heating or cooling power of both the back and the seat independently. When cranked up full blast, the chair only uses 14 watts for heating and 4 watts for cooling, which is a very small amount of energy targeted directly at your body. An occupancy sensor in the seat makes sure that the chair doesn't waste any energy when your butt isn't in it.

Studies have shown that even if the ambient temperature is as high as 86°F, users of the chair report being just as comfortable as if the ambient temperature was 73°F. If you think about that in a larger context, imagine the amount of energy that could be saved if it's 86°F out, but instead of turning on your AC to bring the temperature of your entire home or office down to a comfortable 73°F, you leave the AC off and turn on your chair instead. Essentially, using the chair expands the range of temperatures at which most users report being comfortable, which can lead to energy savings of up to 60%, as measured in a 16 month test in a university office building.

The Berkeley researchers told us that the chairs can also be used to lower energy costs more indirectly. For example, lots of chairs could be networked into a commercial HVAC system, sending data on their use to a central computer. If most people are heating their chairs on a day where the HVAC is trying to lower temperatures, it means that you can turn the AC down a little bit until people switch their chairs off.

imgAdjustable heating and coolingPhoto: Evan Ackerman/IEEE Spectrum

So far, the biggest obstacle to users of this chair is having to remember to plug it in to recharge the batteries. This is where the wireless power comes in: using resonant magnetic fields, energy can be efficiently transferred over a short distance, like from a mat on the ground to receivers underneath a chair. UC Berkeley has partnered with a company called WiTricity to make this happen.

UC Berkeley is already reasonably far along towards commercialization: a company called Personal Comfort Systems is in the process of commercializing a non-wireless version of this chair, called Hyperchair. The technology isn't inherently expensive, and even if you're holding out for the wireless power option, a partnership between UC Berkeley and Staples will hopefully lead to a product within the next few years.

SRI International: Cool Your Heels with ReBOOT, Thermoregulating Footwear

UC Berkeley's climate controlled chair is an awesome idea, but because it's heating and cooling multiple parts of your body, it may not be the most efficient solution. SRI International is focusing on heating only the parts of your body that matter most, by providing temperature control through directly heating and cooling the soles of your feet.

imgPhoto: Evan Ackerman/IEEE Spectrum

What's so special about the soles of your feet? Along with the palms of your hands and some parts of your head, the soles of your feet are made of highly vascularized glabrous tissue, which SRI describes as "the body's radiator." These areas are particularly sensitive to heat flow, which can make temperature changes on just the soles of your feet have a disproportionately significant effect on how comfortable you feel. Experiments at Stanford University showed that active heating or cooling of feet increased the comfortable temperature range of users from 2 degrees C to 6 degrees C.

Direct cooling of your feet (heating has been done for a while) is a complicated technical challenge, since the entire system needs to fit into a shoe to be useful. To give themselves a little more room, SRI is planning on starting with a work boot, called ReBOOT.

Inside the ReBOOT, right underneath your foot, is a thin insole with water channels running through it. Cool water absorbs heat from the glabrous tissue on bottom of your foot, and gets pumped to a heatsink and fan hidden in the sole. The fan blows air over the heatsink and out vents in the sole, cooling the water, which is then sent back around into the insole. Batteries are and electronics are integrated into the sole of the boot as well, and at least in the case of a big fat workboot, the entire system is small enough to fit inside of it with only minor modifications.

imgThis electroactive polymer works as a refrigeratorPhoto: Evan Ackerman/IEEE Spectrum

While SRI has a working system based on existing technology, they're also experimenting with some futuristic enhancements that could make ReBOOT smaller and more efficient. For example, instead of a cooling fan, they've been experimenting with oscillating electroactive materials that move air by flapping like a wing. The turbulent airflow that flapping creates can move more air than a spinning fan, leading to more effective cooling. SRI is also working with UCLA on using an electrocaloric polymer as pumps to move heat into and out of the water in the insole. The polymer has a semi-crystalline structure, which can be aligned with an electric field. When the field is on, the polymer's crystals align, and it conducts heat. When the field is off, the crystals become disordered, and the polymer absorbs heat. This technology has the potential to be an order of magnitude more efficient than existing heat pumps.

Just like with the rest of these ARPA-E DELTA projects, SRI is thinking seriously about commercialization. After work boots, SRI told us that the technology should be able to be miniaturized to fit into other kinds of shoes, meaning that you might be able to benefit from active cooling (or heating) technology unobtrusively, wherever you are, whenever you need it.

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