Archive for May, 2012

Moving Dirt (part two)

Drilling is now underway for our geothermal well field at Hollins for our retrofit of Tinker House.  We’ve scaled it back to 44 wells because, well, we have great dirt.  The technical term would be thermal conductivity, but sometimes it’s just easier to tell folks we have great dirt.

This system differs from E&H’s Brooks Field House because it is a vertical well system (as opposed to horizontal), but the concept is the same.  Sometimes it’s easier to think about geothermal heating as a heat pump, running on the same basic refrigeration cycle I’ve described before.  Your standard residential unit is an air-source heat pump, and this would be a ground source heat pump.  The primary difference is that a geothermal system uses the ground as a heat exchange medium, rejecting heat in the summer and absorbing it in the winter.  An air source system simply rejects to or absorbs from outside air.

The advantage of a ground source system is that the temperature of the earth below the frost line is very stable, usually about 50-60 degrees.  Air source heat pumps become much less efficient as temperatures become more extreme (below 40 degrees and above 85).  This benefits a geothermal system the most in the winter, as many heat pumps need electric resistance heaters to cope with sub-freezing temperatures (although some new systems are now operable to 10 degrees and below).  The typical coefficient of performance of a geothermal heating and cooling system is about 4, meaning for every one watt of energy we put into the system, we get 4 watts of heating or cooling out of the system.  This is why geothermal heating and cooling systems are considered renewable energy; we’re essentially extracting free energy (in the form of heat) from the ground.

The district heating system we currently use has an efficiency of 60-70% when you take into account the efficiency of the boiler, the steam lines and traps, and any leaks in the system.  The cooling system is comparable in efficiency, but the geothermal system (again) has a few advantages.  First, there is no need for a noisy chiller or cooling tower,  Second, geothermal heat pumps have very few moving parts and can last 20-25 years (compared to 15 for a chiller and 10 for a high-efficiency boiler).  Last, but not least, the maintenance of wells is much less costly than that of steam and chilled water lines.

We’ll be measuring performance of the systems once they are in to validate these claims compare their efficiency.


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The Story of Send

Google recently put up a new site explaining what happens to an email after you press send.  It’s an accessible and understandable way of explaining how email works, but the most important part of the story (in my opinion) is Google’s focus on energy efficiency.  Energy costs are a big part of the cost of doing business for all tech companies.  We don’t think about it regularly, but every time you do a Google search, a server in a data center somewhere turns on (or ramps up) and processes that request.  This is only a fraction of a kilowatt-hour and less than a gram of CO2, but if you think about the millions of people performing searches all around the world it starts to add up.  On a larger scale, data centers consume about 100 billion kWh in the US each year at a cost of over $7 billion.

That’s one of the reasons why companies like Google. Facebook, and Apple are aiming to improve the PUE, or power usage effectiveness, of their data centers.  This is essentially a measure of data center efficiency, and is a ratio of server power usage to total data center usage.  A one-to-one ratio is a perfectly efficient data center, but because data centers need a lot of cooling to keep the servers happy the actual PUE of high-efficiency data centers is closer to 1.2, with the industry average closer to 1.5.  Facebook has claimed a PUE as low as 1.07 for its newer data centers, which is the best in the industry.

Tech companies are also incorporating renewable energy in their data centers to ensure reliable power and control costs.  Apple’s new data center will have biogas-powered fuel cells and massive solar arrays, and Google seems to be investing in every wind energy project it can.    With tech companies constantly having to add computing power by building new data centers, the cost of adding renewable energy and extra efficiency measures is a small fraction of the total cost of these projects.  Sometimes what’s good for business is good for the environment too, and so many tech companies are doing these things as part of their normal business operations because it makes sense for their bottom lines.

Check out the video below to see a little more about how energy-efficiency plays a small role in every email you send.

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Moving dirt!

Construction is officially underway for Hickory Hall, E&H’s newest and greenest residence hall.  We’re very excited about this project, and I’m hoping to document as much as possible along the way.  Because this is modular construction, the individual rooms are already being fabricated in a factory and will arrive on a truck later this summer.  Right now it looks like an average construction site, but in a few weeks it’ll look like a giant game of Tetris.


The Brooks Field House is also looking good.  It should be completed in a few short months, but as you can see the roof is now on and the brick facade will be installed soon enough.  I’ll post some pictures of the geothermal well field next week, and also talk a little bit about how the system works.

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Semester wrap-up

Well, it’s been a while since I’ve posted, but I’m back for the end of the semester rush.  Over the past month, I decided to give the blog a rest.  I thought about whether it was the best way for me to communicate my work at Hollins and E&H, and whether anyone was still reading it.  And after this crisis of confidence, I decided that I’d just keep writing anyways and think about using other forms of communication as well.  So, I’ll be back with regular updates (at least weekly) on what’s going on at both campuses.

With that being said, I’d like to congratulate the residents of Stuart and West Halls at  E&H and Hollins, respectively.  Both won their inaugural energy challenges, although both were close contests.  Even though we are small institutions, we helped contribute to the 1.7 million kWh saved during the course of the Campus Conservation Nationals.  It was a great effort from more than 100 schools across the country, and we hope to compete (and win!) next year as well.

Now for some project updates.  Last month E&H broke ground on its latest residence hall, which was designed to achieve passive house certification (read more about PH here).  Like its sister building, Elm Hall, Hickory Hall will be built using modular construction and should be much more energy-efficient than our existing residence halls.  I’ll provide updates during the construction process this summer.  Construction is also well underway for the Brooks Field House, which will utilize a geothermal HVAC system and was designed to achieve LEED-Silver certification.

Not to be outdone, Hollins will be retrofitting its largest residence hall, Tinker House, with a geothermal system as well.  Work is scheduled to start in a few weeks and will wrap up before the students return in the fall.  We’re excited to see how this new system performs and, as above, I’ll be posting pictures along the way.  Until then, this picture of Dana’s solar panels on this beautiful day will have to suffice.

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