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"A society built on green design, sustainable energy and closed loop systems, a civilization afloat on a cloud of efficient, non-toxic, recyclable technology." ~~Alex Nikolai Steffan

9.14.2012

NET ZERO SHOWCASE TOUR

Commission Chair Akinyemi, Commissioner Dozier, Rep Williams and Extension Staff 
 
Will Sheftall, Leon County Extension Staff
Close-up Solar Panel and mini-inverters
 Solar array at Leon County Extension Center 
All Photos by Green Tallahassee
Today's tour at the Leon County Cooperative Extension Center highlighted innovation resulting in energy savings.  A combination of solar panels, a closed loop geothermal system and monitoring by staff can result in an annual  utility usage bill of zero.  

Funded by a grant of approximately $480,000 from the Florida Energy Office from Federal Stimulus funding with match from Leon County, the Leon County Extension Center was able to design and bill a project that resulted in a net zero building.  (the solar array was approximately $300,000 of the total project cost.)

The Extension office building, which is a 50 year old structure, was an unusual candidate to be retrofitted as a net zero building; more common are projects that are new construction.  

The solar photovoltaic panel array of 253 cells, a 60 Kw system, is a fixed installation that is adjacent to the building, rather than on the building's roof.  The system was mounted on the ground as its purpose is pubic education as well as energy savings. It provides a shade canopy over a paved lot used for parking and outdoor events.  It is expected to generate over 78,000 kWh of AC electricity annually, estimated to be equal to the amount of electricity the Center would use in one year.  According to Extension Agent, Will Sheftall, who lead a group tour of the Center, "the system was sized to meet but not exceed the building's annual energy needs.  One of the project's goals was not to produce a lot of excess energy that would be sent back to the City utilities."  Currently, there is no battery storage of solar energy generated.

Staff obtain a computer read-out from each of the individual solar panels so that each panel's performance can be measured over time and so that if one panel is not working, it does not affect the entire system. Some of the panels are shaded by trees, which was intentional.  With the ability to monitor the performance of each individual panel, data can be collected about the energy generated under differing conditions including shade, time of day, time of year, weather conditions, etc. 

The read-out can be summarized to show an estimate of the carbon offset by the system.  Installed in mid-March and running as a beta project until today, data shows that the months of March, April and May resulted in more energy being generated by the solar array than was used.  With the hotter summer months, the system is not generating all of the electricity needs.  However, over an annualized period, the amount of energy generated will meet or exceed energy usage.  The system's savings estimates are based upon the City of Tallahassee Utilities' 'General Service Demand' rate for commercial customers.  Extension staff indicated that the utility bill for August was $5.00, excluding the net peak demand cost that is charged to commercial buildings.   

Each solar panel contains its own inverter (pictured above) that converts DC power into AC, making the system more efficient as it sends usable AC current directly into the building.  

The closed loop geo-thermal system has reduced the cost of cooling and heating the building by 40% and is integrated with an energy recovery hot water heater. The system transfers water from underground where the temperature is between 68 and 70 degrees year round.  When the system is cooling, warmer water is circulated away from the building, transferring the heat into the earth into the well field at the back of the Extension property.  When the system is heating, cooler water is circulated away from the building and absorbs heat from the ground before being recirculated back into the building.  (A second heat exchange takes place in the building's mechanical room.)  In addition, the building's conventional electric water heater was modified to recover the geothermal waste heat.  

The project was a finalist in the 2012 Sustainable Florida Best Practice Awards in a field of nearly 90 nominations.  

The Leon County Extension Center, located at 615 Paul Russell Road in Tallahassee, is an education facility and is open to the public for tours, educational classes and technical assistance.

Leon County has committed to completing energy efficient projects including the new Eastside Branch Library which is a LEED certified energy efficient building.  

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