SunDog Solar Thermal Test Site

Science Experiment– Effects of running HTF to shed frost

sundogsolarexperiment — Fri, 18 Dec 2009 15:53:55 +0000

Last night was extremely cold. When I arrived at the test site at 8:40 this morning, the temperature was 8 degrees Fahrenheit, and all four test arrays were covered with a thick layer of frost.

I decided to take advantage of the weather conditions to run a test. We have long noticed that the flat plate collectors shed frost and snow more quickly than the evacuated tubes. I attempted to measure the speed at which this occurred.

At 8:47, I set the pumps on “Automatic on” to run heat transfer fluid through the arrays. Before 8:47, they had been in the “automatic” setting, and not running, due to the low levels of sunlight and the low ambient air temperature. The heat transfer fluid was 71 degrees F, and the outside air temperature was 8 degrees F. All four arrays were covered in a think layer of frost.

At 9:31 AM, I checked the arrays. The evacuated tubes (both the Gomons and the C4 array) were still covered with a moderately heavy layer of frost. The flat plates (including the plate in the hybrid array) showed signs of thawing. About 40% of the area of the flat plates was completely clear of frost, and about 60% was covered by only a light coat of frost. The completely thawed areas were horizontal bands that correspond to the copper tubing that carries heat transfer fluid through the flat plates. The ambient air temperature was 11 degrees F, and the HTF was then 81 degrees F.

At 9:53, the flat plates were completely free of frost. The evacuated tubes and the C4 tubes showed slightly less frost, especially on their eastern side. The ambient air temperature was 13 degrees F.

-Luke Forster

Visit from NYSERDA and New Generation of SolarWave Software

sundogsolarexperiment — Thu, 17 Dec 2009 17:01:04 +0000

The past few days at the SunDog Solar Thermal Test Site have been extremely busy.

Yesterday afternoon, six representatives from NYSERDA (N Y State Energy Research and Development Authority) paid us a visit. A professor of mechanical engineering from Union College also visited. We gave our guests a full tour of our facility, showing them our new 25kW PV array, our used vegetable oil boiler, the new solar thermal mobile lab, and our rooftop arrays. We also had a meeting where we presented an overview of our test center and an analysis of some of our collector data. We had a stimulating and insightful discussion about how different aspects of a solar hot water system affect performance, including the nature of the collector and glazing (flat plate vs tube, single wall vs double wall), flow rate, and inlet fluid parameters.

Around noontime yesterday, SolarWave released its latest generation of monitoring software. I am extremely impressed with the appearance of the new site and the new features and functionalities. SolarWave’s programmers and IT specialists are currently working on de-bugging the software.

As we are simultaneously updating our sensor system and our web-based monitoring system, we are encountering various snags and difficulties. Most importantly, our Evacuated Tube Return sensor seems to be problematic. I will remove the ET sensor line from the roof this afternoon and mail it back to SolarWave for repair or replacement.

Weather at the site remains dry and bitter cold. We think that tomorrow will be mostly sunny.

-Luke Forster, SunDog Solar

New Sensors Installed and Plumbing Changes

sundogsolarexperiment — Thu, 10 Dec 2009 20:44:46 +0000

We are continuing to make improvements and changes to the test site.

Today, SunDog Solar employee Steve Mammoser installed a new, larger expansion tank on the system. Since we are increasing the number of collectors on the roof, a larger expansion tank is a necessary component.

Luke Forster and Dave Ohls of SunDog Solar installed the new sensors, sensor boxes, and wiring for the four arrays. Peter Skinner of E2G Solar helped change the piping to accommodate the new arrays that we will be adding in the near future.

I am working with SolarWave Energy Inc to make sure that the sensors are properly installed and are functioning properly.

The weather today was cold and windy, with temperatures in the low 30s for most of the day. Since we are working on the sensors today, the monitoring system did not log any data for the day.

I took pictures of the sensors and wiring setup.

-Luke Forster

Thermowells Installed

sundogsolarexperiment — Tue, 08 Dec 2009 21:00:44 +0000

This afternoon, Luke Forster of SunDog Solar and Peter Skinner of E2G Solar finished installing a series of thermowells on our test arrays. These thermowells will house our new, high-quality matched sensors. We will install the new sensors in their thermowells over the next two days, and will continue to improve the data collection and transmission firmware. SolarWave Energy Inc is shipping us a set of new sensor boxes within the next day, and we will install them as soon as convenient.

Next week we are meeting with representatives from NYSERDA (N Y State Energy Research and Development Authhority) to discuss the status and performance of our test center, and our plans for expanding it. We look forward to meeting with them and their guests and discussing our data. We expect that our new sensor and monitoring system will be fully installed and operational for their visit.

NOAA predicts that the test site will receive snow over the next several days.

-Luke Forster

Update- December 7, 2009

sundogsolarexperiment — Mon, 07 Dec 2009 19:46:58 +0000

The test site has survived the first snowstorm of the season. At 2:30 PM today, Luke Forster examined the sensors, sensor boxes, and site hardware for ice damage and infiltration. The arrays are in good shape, and I do not expect any weather damage problems.

Both evacuated tube arrays remain partially covered in snow and ice, although the snow fell on December 5. I estimate that the lower 18 inches of the tube sets are covered in snow. The flat plates remain free of snow, due to their smooth flat surface and their ability to re-radiate heat.

We expect to receive our new set of matched sensor pairs from SolarWave this week. We have prepared a set of thermal wells, and will install the new sensors as soon as possible.

Production has been low over the past week, due to cloudy weather and low levels of seasonal radiation. The flat plate and the hybrid arrays continue to produce more BTUs than the evacuated tube arrays on most days. The supposed negative production of the C4 array on December 2 and 3 appears to be a data error.

-Luke Forster

Production Update: November 9, 2009

sundogsolarexperiment — Tue, 10 Nov 2009 14:23:25 +0000

Partial cloud cover limited production yesterday, especially after noon. As we approach the winter solstice, the amount of solar radiation will continue to fall, due to the lower azimuth. Winter snow clouds will also hamper production.

We have had very little frost to date. Frost poses a minor obstacle to morning production, since sunlight can not pass through the frost to the absorber. The frost must be melted, either by sunlight or by warm heat transfer fluid passing through the collectors. The flat plates melt frost quickly, since they re-radiate moderate amounts of heat. The evacuated tubes melt frost more slowly, since the vacuum in the tube prevents heat transfer through convection and conduction.

Daily Production Totals:

Flat Plate: 35,650 BTUs

Hybrid: 27,100

Solaqua Evacuated Tubes: 27,260

C4 Evacuated Tubes: 20,355

In terms of daily production and hourly production, the flat plate collectors outperformed the hybrid array and the evacuated tubes. Over the past eleven months, the flat plates have very frequently outperformed the other arrays. In recent weeks, it appears that the hybrid array was outperforming the flat plate array- however, I suspect that such data might be influenced by sensor anomalies.

Monday, November 9

-Luke Forster

Production Update, November 5, 2009

sundogsolarexperiment — Thu, 05 Nov 2009 16:29:54 +0000

We are continuing to work with SolarWave Energy Inc to resolve our sensor precision issues. The staff at SolarWave is preparing matched sets of thermocouples, which should provide the site with more accurate and reliable data. We intend to insert the thermocouple sensors directly into the arrays’ heat transfer fluid via thermowells. In the current setup, the sensors are attached to the outside of the copper piping. We expect that the upcoming system will more accurately measure temperature data.

Over November 2-4, Peter Skinner of E2G Solar and Luke Forster and Betsy Wyman of SunDog Solar presented a three-day solar thermal installation course at Bronx Community College. We referred to the SunDog Solar Thermal Test site and its monitoring system in our discussions on collectors and monitoring equipment.

Yesterday was fairly sunny in the morning, and cloudy in the afternoon. The temperature was mild, and remained in the low to mid 40s for most of the day.

Daily Production Totals, November 5, 2009

Flat Plates: 27,325

Hybrid Array: 34,930

Solaqua Evacuated Tubes: 26,975

C4 Tube Array: 23,295

Again, the hybrid array recorded more BTU production than the other arrays. However, we are reluctant to fully endorse this data, owning to our current sensor issues.

-Luke Forster

Site Update- Monday, October 26

sundogsolarexperiment — Mon, 26 Oct 2009 19:44:09 +0000

The weather at the test site today was generally sunny, with mild temperatures.

We experienced heavy rain over the weekend on Saturday, and Sunday was mostly sunny.

We are currently experiencing difficulties with the monitoring system, and the C4 array sensors were down over the weekend. As of 3:30 PM today, we believe we have restored C4 sensor functionality.

-Luke Forster

Production Data- October 19-20

sundogsolarexperiment — Fri, 23 Oct 2009 15:23:11 +0000

Monday October 19 was a sunny, clear day. All four arrays performed well, and gathered many BTUs. The 20th was partly cloudy, with intermittent sunlight.

Daily Production Totals- October 19 (9AM-6PM):

Flat Plate Array: 61,819 BTUs

Hybrid: 72,885 BTUs

Solaqua Evacuated Tubes: 52,285 BTUs

C4 Evacuated Tubes: 46,251

The hybrid array gathered the most BTUs over the day. I find this very surprising, since the flat plate array typically produces the most BTUs on sunny days. It is most unusual that the hybrid array is producing 11,000 more BTUs than the flat plate array. I wonder if either the flat plate or hybrid array’s sensors were damaged during the boiling water and ice bath tests.

The hybrid array consists of one flat plate and one set of Solaqua evacuated tubes (the same ones used in the flat plate and evacuated tube arrays). The average production of the flat plate array and the evac tube array on the 19th was 57,052 BTUs. This is nearly 16,000 BTUs less than the hybrid array registered. Although we suspected that there might be a positive synergistic effect in the hybridization of the plate and tubes, I suspect that is not enough to account for such a large discrepancy.

October 20th Daily Production Totals: 9AM-6PM

Flat Plate: 14,979 BTUs

Hybrid: 15,785

Evac Tubes: 8,409

C4: 13,816

The hybrid array again out-performed the other arrays. The C4 evacuated tube array also performed well. The C4 array consists of double-walled evacuated tubes, which tend to perform well on cloudy days.

-LF

61819

Possible Link Between Flow Rate and HTF Temperature

sundogsolarexperiment — Fri, 23 Oct 2009 14:34:40 +0000

I noticed something curious about the flow rates at the test site.
The pumps have been running on automatic recently, and It appears that
the fluid is running at different speeds based on its temperature. On
Oct 19, the hybrid fluid was running at 2.3 gal/min at 50 degrees, and
3 gal/min at 135 degrees (see attached graphs). The other arrays show
a similar pattern. This seems to be a recent phenomena- in past
months the flow rates held steady, regardless of temperature.

Is this a sign that the heat transfer fluid is getting slushy? We
have been running the fluid at very high temps recently. At high temperatures (over 200 degrees), the propylene glycol antifreeze tends to break down.

Note the changes in flow rates

We will look into this.

-Luke Forster