Tuesday, December 22, 2009

A Temperature Measurement Issue

One of the major issues in the climate change discussions is the reliability of the historical temperature records. The sceptics pounce on this one, and frankly, I have to give them some credit, because I've spent a good deal of time looking into the temperature data, and understanding some of the nuances isn't necessarily easy. In fact, I'm not convinced that the scientific community at large understands this as well as they need to. This is not to say that I think the carbon issue is a non-issue, but I would not be surprised if a significant part of the measured warmth is not due to greenhouse gases but to other things with the measurement problem being one of a myriad of outstanding analysis wrinkles.

The graph above is a rather extreme case in point. This is a plot of the outside temperature data as measured at our house and nearby. The light blue line is the temperature measurement from the thermometer associated with my generator, and a reading is taken every 15 minutes. The outside temperature is measured mainly to make sure the fuel balance is correct. I'm using the data to help understand the expected heating load.

The data are from 31-Mar-2009. Last spring I was outside and remember seeing that the sun was shining directly on the box that is attached to the back of my house and which contains the temperature reader. Most of the year this side gets shaded by three trees, but in the spring, prior to the leaves coming, the sun will peek through to the back side of the house in the late afternoon. When that happens, the process of radiative heating warms up the box beyond the ambient air temperature. I remember at the time thinking I needed to check the data for this, and well, I guess the effect is pretty big.

The other data are from the Weather Underground site. There are data from literally thousands of personal weather stations available there now, and I picked the closest stations to my house that had data on the appropriate date. There are two green-colored datasets, one of which is missing most of the data (and is the straight line across the plot). The second one is closer to the beach, and that is the primary reason it is lower in temperature. The others are further from the shore and more representative of our experience--except for the late afternoon when the sun hits our thermometer.

Alas, another thing that needs to be checked and corrected.

Just for the record, no I don't think all the NOAA (and other scientifically oriented) thermometers drift by as much as 20 degrees F, but I would not completely rule out issues at 1/20th that size, and this comment is based on not this particular graph but on my own experience dealing with NOAA data as well as other International data. Yes, there is a whole sub-industry involved in this academically, and yes they do good work, but I don't think the issue is as closed as many believe it is.


Thursday, December 10, 2009

Power Source--Relative Contributions

As an addendum to the last post, the figure above shows the relative fraction of the different power sources. Solar varies between 10 and 15 percent of our power that we use. The big shift is when the Ecopower was installed. We now co-generate locally between 25 and 85 percent of our own power depending upon the heating needs with the largest local generation naturally being in the winter. Combined with the solar, during the swing heating months we generate virtually all of our power locally.

For completeness, the two vertical lines show important operation changes. The first is when the solar panel upgrade occurred (can you tell the difference?! It sure is hard!). The second is when we switched the Ecopower from 2nd stage heating to first stage heating. The plan is to keep it that way at least through this coming winter with no other changes.

Friday, December 04, 2009

Household Energy Use

With the digitization of the propane data as described in the last post, the total household energy use can now be analyzed. This kind of analysis seems to be growing in popularity. Witness the rise of Google Power and Microsoft Hohm. The latest one I've been introduced to is www.mygreenquest.com. I've looked at the last one and may migrate some material there, but for now, I'll use my own clunky analysis program as there are only so many hours in a day.

The following figure shows the fuel use for our house since late 2000. The dark blue is heating oil, the light blue is propane, and the big purple vertical rectangle is the period where we gutted the house and expanded it from 2600 to 4200 square feet. The size addition, I think, now files inside the "what were we thinking" folder, but we do love our home. Below the fuel figure is a figure detailing the electricity use and generation.

In the household fuel use figure, the different rectangular boxes represent one delivery by the distributor(s). The use clearly spikes in the winter and deliveries are more frequent then, so the rectangles are narrower. The base load is easy to estimate at 1.9 gal/day for heating oil--independent of time amazingly--and the propane use is 3.9 gal/day. The difference between those two numbers is discussed in the post prior to this. (That post is unfortunately a little technical and its significance is probably only appreciated by the makers of the Ecopower and maybe a few other pointy-headed geeks such as myself.)

The electricity figure is a little busy but full of information. The upper black line is the total amount of electricity consumed with the blue infill being the amount pulled from the grid. The yellow infill is solar generation, and the green infill is the Ecopower co-generation.

The number of different operation modes is beginning to become a problem in analyzing the data. Here are some of the details. Prior to the renovation, the situation was the standard old New England drafty house, poorly insulated, heat came from heating oil with supplemental electric heaters, and power all came from the grid. Just after the renovation, the solar panels were installed (2.5 KW) and they were upgraded in Sep '08 to 3KW. The Ecopower co-generator went live in Apr '08. In the fall of '06, after the renovation and after the hot summer, the geothermal (ground source heat pumps) were installed. Needless to say, this is a very non-standard situation here. One further complication is that prior to 2009, the system was run with the geothermal as first stage heat and the Ecopower as second stage heat when the geothermal couldn't quite keep up with the heating load. Since Jan, 2009, the situation is reversed with the Ecopower as first stage and the geothermal brought on only when the Ecopower can't keep up with the heating load. Very non-standard indeed.

The above figure shows the data from 2006 and is an attempt to better see the detail. The co-generation contribution is encouraging, but it comes at a cost of more fuel consumption. It seems like we are in a game of whack-a-mole here. We put in geothermal in an effort to reduce heating oil dependence only to see the power consumption go up. We put in solar, and while it helps, it sure seems less than stellar (I guess that pun was intended). Co-gen works at reducing electricity from the grid, but now we burn more fuel.

The question now in my mind is whether or not the move to propane and local generation was what I wanted, for it means more fuel consumption, or at least it seems that way. A primary aim is to reduce foreign energy dependence and increase our energy security, and given that as the goal, is burning propane, which has some foreign sourcing, better than burning natural gas at a power station and running geothermal off the power which is almost all domestic in origin? I think I've resolved how to think about that issue beyond (1) the efficiency argument that the grid structure is enormously inefficient, and (2) local power capability represents an improvement in energy security (even if it has yet to be enabled for backup power mode). These issues and more will be the subject of a later post.

When analyzing the last figure, there are two things worth mentioning. The first was alluded to earlier, and that is prior to 2009, the Ecopower ran in second-stage heat mode with geothermal as first stage. The drop-off in grid power since 2009 is substantial and installations would reflect a drop, but remember that the drop is in part from a reduction in heating with geothermal. The second item regards the small spike in heating oil use in Mar, Apr, 2008. Seeing that brought back some memories.

Throughout the winter of '07-'08, the exact Ecopower installation time was somewhat uncertain. As a result, I was ordering heating oil in 100 gallon units from a local distributor, the minimum amount they would deliver, for I didn't want to be stuck with extra oil. Timing wasn't always good, and we ran out a couple of times. With geothermal available, we had house heat but not water heat, sometimes for as long as 24 hours, much to the consternation of an increasingly impatient family. The experience was valuable for it taught us that having hot water is an enormous contributor to one's self-esteem and without it, life can appear less than dignified.

In early '08, as the Ecopower launch was getting closer, the heat was switched to heating oil as first stage heat to insure we wouldn't get stuck with any extra oil, and the spike in heating oil use is with the house just on heating oil. That period of 2 fills provides us with a powerful comparison between the old house and the new one, and the new house on heating oil still used less than the old house on heating oil, degree-for-degree, even though the house is now considerably larger.

At the tail end of the heating oil period, with the heating season over, we only needed hot water heat, and it made no sense then to buy 100 gallons from the distributor. It was funny interacting with them. Prices were soaring during that period, and I think they thought I wasn't able to afford too much oil, which was the case for many people, because we were only buying to 100 gallon increments instead of filling our tank. They knew I was in the process of getting off heating oil, and when heating oil went above $4/gal, the drivers started asking me about how the geothermal was working. It was an interesting turn of events that the people whose income depended upon a system of fossil fuels was beginning to question the value of it.

The last little heating oil fill is actually me filling it 5 gallons at a time with diesel from the gas station. We still have about 5 gallons of heating oil (diesel really) in our tanks. Some day we'll remove all vestiges of the heating oil system. Whenever we get around to it, that will be a good day.

Labels: , , ,