Alfred State College is a hands-on technical college in Wellsville, NY and part of the SUNY system. Beginning in 2010 and finishing in 2011, the students built a 2000 square foot “zero-energy” home on campus. The concept of the home is to be a long term demonstration and research tool for the students and the public on green construction methods and renewable energy systems.
The renewable energy systems included in the home are an 8.8 KW roof mounted Solar PV system, an 8 collector tube Solar Thermal system for hot water production, a 3-ton, 4-bore hole Geothermal system for HVAC, and a 2.5 KW wind turbine.
In order to collect, log, and view data for the home and to control various loads in it, Alfred looked for a monitoring and control solution that would suit them for the long term. A chance meeting at IMT Solar in Buffalo, NY brought the two organizations together. Some of the IMT Solar personnel had vast experience in Industrial Automation and knew that a PLC based solution like ‘REVTOS’ would give Alfred everything they were looking for, as well as the expandability for future system add-on’s.
IMT Solar designed the system around two control enclosures containing micro-PLC’s, dedicated touch screens in each enclosure for local viewing of the data, and the home’s Ethernet network infrastructure. Additionally, a 23″ touch screen PC was added in the main visitor area of the home for viewing by all visitors. Built in web servers allow access to the data across campus and across the internet via a web browser.
Students and visitors are able to see the direct relationship between solar irradiance and the current output of each string. The can also compare the irradiance to the total DC output of the 8.8 KW array.
By using silicon irradiance sensors instead of pyranometers, the IMT Solar system is able to show the real time data in 1 second intervals. As this graph shows the irradiance level (and therefore the system power output) can change very, very quickly. It also shows how in a well-behaved system the power output follows the irradiance level very closely on an instantaneous basis.
When students noticed the current output on string 4 dropping well below the other strings, they knew something was wrong. A look through the web cam showed that at this time of day, a small amount of shading from the higher roof was reducing the output on string 4. The students had studied the impact of shading on solar PV systems, but this was the first time they could see the data first hand. The differing roof elevations was known to be a problem at the start of the project, so the students designed the solar array into two part, going through two inverters so that the whole array was not dragged down by early morning or late afternoon shade.
Four different grouts were used to backfill each of the four vertical bore holes. To study the long term differences in the thermal conductivity of the different grouts, the students embedded four temperature sensors in each hole so they could compare the temperatures at the same levels in each bore hole. IMT Solar shows all these temperatures in real time values as well as a graphical format. Power meters were also utilized to study all the power and energy characteristics of the three different parts of the system…the heat pump, the backup resistive heater, and the heat recovery system.
For each renewable energy system, IMT Solar tried to embed a brief tutorial on how the system works, as well as the specifications for the exact system used in the home. This gives the many visitors who tour the home a better idea of what each system is and how it works, and the new students key information on the specs of each system
IMT Solar encourages putting key system information right on the screens. These are typically drawings that would typically be lost somewhere in a three ring binder. Here the autocad drawing of the PV electrical system becomes one of the screens, with live data embedded right on it. It allows students to show new students and visitors how the system is wired. It also allows them to quickly diagnose problems in the electrical system. A similar screen was done for the string map…showing exactly which solar modules are in each of the four strings.
IMT Solar used a total of nine power meters in the overall system. Three measured the power and energy characteristics of the power produced by the two PV and one wind inverters. Five were used to measure the power and energy characteristics of the Geothermal and Solar Thermal systems. And the final one was used in the main electrical panel of the house as a net meter, to show the accumulated energy pushed or pulled from the grid.
IMT Solar was enrolled as an entry in Siemens TIA Portal Application of the Year contest for 2012 as a result of the Siemens hardware and software products utilized in the Zero Energy Home project at Alfred. IMT Solar ultimately won this award, taking first place across the entire USA. Here Tim Lehner, the local Siemens sales representative presents the award to Dave Kostick and Tim Klein of IMT. Dean Craig Clark looks on as the Zero Energy home gets yet one more key point of recognition a year after being “opened for business”!