Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts
Sunday, September 4, 2011
A Memorial for my Refrigerator
When she was born, I was a boy. I walked three blocks to my neighborhood school every day to attend the sixth grade. My teacher's name was Ms. Skaros. The Rubik's Cube had just been invented, and the hot new teen fashion style was "preppy." My voice hadn't broken yet. My "girlfriend" was Anne Schultz.
"The Wall" was still hugely popular, although "That Wall" had not yet been torn down. The military action of the day in Afghanistan involved the U.S.S.R., not the United States. Rambo had just tasted his First Blood. The Officer was just becoming a Gentleman.
James Rockford could have put his $0.79/lb steak in this refrigerator. The Muppet Show could have had one of these refrigerators in their green room. The Talking Heads hadn't started making Stop Making Sense yet.
A handful of computers existed on the "Internet," although the web was still a decade to come. The hot new computers were from IBM and the software was from Wordstar. Microsoft Word hadn't been invented. Pac Man was the video game craze. Apple's new Lisa computers were a flop.
The big Packer's "B" was Bart, not Brett. The Milwaukee Brewers took their only trip to the World Series.
Pioneer 11 had encountered Saturn three years before, paving the way for Voyager 2's first real close-up and color pictures of this ringed planet and its moons. The controversy over how fast our universe was flying apart was starting to rage.
This is the world my refrigerator was born to in the year 1982. Someone else purchased this refrigerator then to keep their vittles cold, and I inherited it. Now it is time to move on to a more efficient and useful one. May she rest in pieces at the landfill.
Sunday, October 5, 2008
I'm Not a Physicist, but I Play One on TV
If you watch television, you might have seen two separate advertisements -- one for high-end LCD televisions and the other for solar panels -- but both are from the same company, Sharp Electronics Corp USA. This summer they began a major advertising campaign for both products, as unrelated as they might seem, as life changing products. Both feature a curious white-haired academician expounding the virtues of Sharp's wares.
The LCD television commercial starts like this, (video)
Seems like you need to be a physics professor to choose the right TV. Luckily, I am one. ...while the solar panel pitch begins, (video)
I'm an astrophysicist, a star gazer, but here's something cosmic I discovered on earth, ...
Both commercials are narrated by a flaxen-haired, well-dressed man, identified by the caption "Professor Gerard Fasel, Astrophysicist." Who is this man? Is he really an astrophysicist? Read on, you may soon know him better as "Albino Security Guard."
Dr. Fasel is indeed listed on the faculty at Pepperdine University as a "Visiting Professor." His college biography lists courses taught in physics, mathematics and astronomy. He also appears to have teaching ratings at ratemyprofessors.com for the years 2003-2008, so we can assume he has been teaching at least part-time for most of that period of time.
However, according to Dr. Fasel's list of publications in the subjects of physics and astrophysics, his last publication of any sort was in 1995, or 13 years ago. The article, "Dayside poleward moving auroral forms: A statistical study," was published in the respected Journal of Geophysical Research. During his academic hayday of 1992-1995, he published a total of four refereed publications, either as primary author or co-author. All of these publications regard the study of terrestrial aurora, which is in essence a study of the interaction between the solar wind, earth's magnetosphere, and upper atmosphere. By the way, the phenomenon of terrestrial aurora, while very interesting, has virtually nothing to do with what I would call astrophysics, nor with solar-electric power.
But Fasel is much more than an academic! Dr. Fasel's acting career, as listed by IMDB has shown much more activity. In the past six years he has had four significant acting parts, both in television and movies. His next role will be in the movie The Truth About Angels, due out in 2009, where he plays the coveted albino security guard role. I'm sure Rutger Hauer is howling mad that some physicist beat him to the punch!
Sharp Electronics is proud of its spokesperson. In a press release on July 14th, 2008, announcing their campaign, they wrote,
... The commercial will feature Professor Gerard Fasel, a visiting professor of math and physics at Pepperdine University. With a PhD in Physics and a sophisticated and engaging persona, Professor Fasel lends a scholarly credibility to the new solar and LCD commercials.The important words here are "lends a scholarly credibility." Based on his scientific publishing record, my opinion is that Dr. Fasel is no longer an active researcher in science, and indeed has spent more time acting in the past decade than publishing research papers. I think it's pretty clear that he is not an astrophysicist, since none of his articles discussed astrophysics. For that matter, he has not published work related to solar physics, televisions or solar panel technology either. I don't doubt that Sharp took the time to give Dr. Fasel a tour of the manufacturing plant and its technology development labs, and Fasel probably has a reasonable understanding and appreciation of the physics that goes into the technologies that he is advertising. But judging by his research and teaching history, I doubt that he has any better skill choosing a television or a solar panel than your average Joe Sixpack.
In my opinion, he is simply an actor -- a spokesmodel -- hired by an advertising firm and used to make the company's technology seem more credible. They hired him for his interesting looks, his personality, and yes, the three letters "Ph.D." at the end of his name. Couldn't they just have easily hired him to do a commercial for medicine? Hmm, I think I could write the script...
EXPERT: Seems like you need to have a Ph.D. to understand cold remedies these days. Luckily I have one. ...Oh Dr. Fasel, will you star in my commercial?
(Photo credits: lifechangingbox.com; Sharp Corporation, 2008)
Wednesday, September 3, 2008
Unstable Physical World
A very interesting paper just appeared on the arxiv.org preprint server. It presents the work of two different groups measuring the radiactive decay rates of two specific isotopes, Silicon-32 and Radium-226, who found some strange and intriguing results indeed.
Scientists believe we live in a universe where physical "laws" apply the same everywhere. It shouldn't matter whether we are on the earth, the moon, or the depths of outer space, the equations and theories should be the same. Radioactive decay is governed by the so-called "weak force," which is in principle a nuclear-scale force that shouldn't really care about the anything beyond the nucleus itself. So it is natural to expect that Silicon and Radium should decay radioactively at the same rate wherever we find it.
But that's not what was found by Jenkins et al. in their analysis. Taking data from two different laboratories, at Brookhaven National Laboratories in New York State and another in Germany, the authors found the decay rate goes up and down with an annual cycle. See this blog entry for a graph. The variations are less than a tenth of a percent over the course of a year for both radioisotopes.
The authors speculate that the effect is dependent on the distance between the sun and earth, which also has an annual periodic modulation as the earth moves in its orbit between perihelion and aphelion. Of course, this would violate our precepts about the physical laws governing radioactive decay. They further speculate that this may be due to a changes in the amount of solar neutrinos that reach the earth, which might somehow modulate the nuclear decay rates. Or, perhaps it is a variation in the "fine structure constant" with distance from the sun (the fine structure constant dictates the strength of the weak force).
However, if you look closely at the graph, you will see that the radioactive decay rates and the distance variations do not match up quite that well. In fact, the measurements lag the distance template by a few months. I can't imagine what force law could describe such an oddity, but it is definitely not a simple distance relationship.
An experimenter needs to be worried about subtle biases. Both of the experiments were done in the northern hemisphere. Perhaps there is some kind of earth-bound seasonal effect? For example, there could be seasonal temperature variations that affect the sensors. Or, it could be something even more subtle, like annual changes in the cosmic ray flux which affect detector dead-time. An interesting test would be to use a southern hemisphere lab where any seasonal biases would be reversed. There have been some other spectacular results which have been later retracted due to failure to account for equipment (mal)function. A famous example of this was the discovery of a 2000 Hz optical pulsar in Supernova 1987a, which later turned out to be electrical interference from another piece of equipment. These people are not dumb, it's just that the physical world can be more complicated than the ways we can control.
It's worth noting that this paper has apparently not yet been refereed. It's quite possible that during the refereeing process, a lot of these points will be addressed, or the conclusions of the paper might change. Until then, it's still a quite fascinating result!
Scientists believe we live in a universe where physical "laws" apply the same everywhere. It shouldn't matter whether we are on the earth, the moon, or the depths of outer space, the equations and theories should be the same. Radioactive decay is governed by the so-called "weak force," which is in principle a nuclear-scale force that shouldn't really care about the anything beyond the nucleus itself. So it is natural to expect that Silicon and Radium should decay radioactively at the same rate wherever we find it.
But that's not what was found by Jenkins et al. in their analysis. Taking data from two different laboratories, at Brookhaven National Laboratories in New York State and another in Germany, the authors found the decay rate goes up and down with an annual cycle. See this blog entry for a graph. The variations are less than a tenth of a percent over the course of a year for both radioisotopes.
The authors speculate that the effect is dependent on the distance between the sun and earth, which also has an annual periodic modulation as the earth moves in its orbit between perihelion and aphelion. Of course, this would violate our precepts about the physical laws governing radioactive decay. They further speculate that this may be due to a changes in the amount of solar neutrinos that reach the earth, which might somehow modulate the nuclear decay rates. Or, perhaps it is a variation in the "fine structure constant" with distance from the sun (the fine structure constant dictates the strength of the weak force).
However, if you look closely at the graph, you will see that the radioactive decay rates and the distance variations do not match up quite that well. In fact, the measurements lag the distance template by a few months. I can't imagine what force law could describe such an oddity, but it is definitely not a simple distance relationship.
An experimenter needs to be worried about subtle biases. Both of the experiments were done in the northern hemisphere. Perhaps there is some kind of earth-bound seasonal effect? For example, there could be seasonal temperature variations that affect the sensors. Or, it could be something even more subtle, like annual changes in the cosmic ray flux which affect detector dead-time. An interesting test would be to use a southern hemisphere lab where any seasonal biases would be reversed. There have been some other spectacular results which have been later retracted due to failure to account for equipment (mal)function. A famous example of this was the discovery of a 2000 Hz optical pulsar in Supernova 1987a, which later turned out to be electrical interference from another piece of equipment. These people are not dumb, it's just that the physical world can be more complicated than the ways we can control.
It's worth noting that this paper has apparently not yet been refereed. It's quite possible that during the refereeing process, a lot of these points will be addressed, or the conclusions of the paper might change. Until then, it's still a quite fascinating result!
Saturday, January 12, 2008
The Thermodynamics of Heating a House
Follow along as I explore trying to make my house a little more energy efficient, look at my energy usage history, and do a little thermodynamics. There will be some small equations, but I'll explain them in words as well. At the end, I discover something about the insulation efficiency of my house.
I live in a region which is heating-challenged. Every house or apartment I've lived in has had issues with heating in the winter and cooling in the summer. Builders in this area just don't seem to get that a little insulation goes a long way. For my current house, the homeowner's association also decided in its infinite wisdom that it would rip out all the old oil-fired boilers because they were too expensive, and replace them with electric baseboard heaters, because they are more economical. Whatever insane reasoning that led to that decision is now negated, especially since electricity has doubled in price over the past two years here. While it is true that electric heaters themselves are 100% efficient, the power plant and transmission lines are not. Furthermore, baseboard heaters tend to be mounted on outer walls below windows, so much of the heat can be conducted through the wall and escape the house.
I'm trying a few new strategies to try to make my house more comfortable, given its current limitations. First, I added transparent window films to almost all of the windows. The idea is that they hold an still pocket of air against the window, which adds an extra insulation factor. They also can contain small drafts so that cold air can't get in. It does take some work to install them, which basically involves stretching a huge sheet of saran wrap onto double stick tape mounted on each window frame, but eventually I developed a pretty efficient method (especially for smoothing the wrinkles).
A second thing I did was install curtains in the living room doorways, in order to keep the heat from escaping to colder parts of the house from the room I use most. These are cheap but heavy curtains I got on sale at Wal-Mart, hung from an expandable shower curtain rod across two doorways. Finally, I put some foam-board over my back door. It's a thin wooden door that conducts a lot of heat out.
I think these efforts have helped in a very qualitative sense. The living room is much less drafty, especially near the windows. Before installing the films, a cold down-draft from the windows would collide from an up-draft from the heaters to make chilly turbulent zone right where I was sitting. These drafts are gone now. The curtains also definitely help keep the heat where I appreciate it most.
Comfort is good, but I'd also like to know if this is saving energy and money.
PEPCO kindly puts my energy usage history on each bill, so it was a matter of collecting a few old bills and entering them in the computer. That's shown in black below (click for larger image).
The plot shows the number of kiloWatt-hours I use each month (ignore the red and blue curves for the moment). Unfortunately, I don't have data yet for December, the first month that I installed the window films or curtains, so I have to put the efficiency question on hold for now.
I decided to check out this plot a little more carefully. I use the greatest energy in the winter, obviously for heating. There are also small bumps in the summer, corresponding to cooling. Up until recently, I had a very old air conditioner which I rarely used, so my cooling expenses have never been large.
What to compare this with? Well, the there is a nifty number called a heating degree day used for heating calculations. Basically, any day that the mean temperature dips below 65 degrees Fahrenheit is considered a "heating day," and for that matter when the mean temperature is above 65 it is a "cooling day." The number of heating degree days is the number of degrees the mean temperature is below 65. The US National Climatic Data Center (not to be confused with the Climactic Data Center! Ooo la lah!) provides tabulated historical heating and cooling degree day data. The monthly total heating and cooling degree days are shown in the above plot (red=heating; blue=cooling; averaged over Maryland & Washington DC).
It's no big surprise that the heating and cooling curves match up with my energy usage pretty well. It's physics after all.
In fact, the Mr. Quantitative in me wants to do more. I decided to perform a linear regression between these quantities, with energy usage per day as the dependent variable, and heating/cooling degree days per day as the two independent variables. The simple function I tried was:
E = Constant + H(Th) + C(Tc)
where H(Th) is some function of heating degree days (per day), and C(Tc) is another function of cooling degree days (per day), both of which describe power usage versus temperature. This equation has the interpretation that I use some constant electric power all the time (for lights, water heater, etc.), plus the amount I use for heating and cooling, which depend on temperature.
The obvious choice is to make the two electric heating functions, H and C, proportional to temperature. However, I found that wasn't a good fit, as you will see below. Instead, there is an activation threshold. For small temperature excursions, no heating or cooling is required, and I don't use energy. This would be my comfort zone, the temperature range I'm willing to tolerate. I imagine I have a larger comfort zone than many people. As the outside temperature gets more extreme, then I use energy to maintain the inside house temperature within the comfort range. This function can be written as a constant when the heating/cooling temperature is within the comfort threshold, and a linear function outside of that. The linear coefficient of the function describes the number of kiloWatt-hours per day needed to heat (or cool) the house one extra degree Fahrenheit.
The fit works quite well, and here is how the results look. On the heating side, the function H(T) looks like this:
This means that I am willing to tolerate mean outside temperature drops of about 6.5 degrees (F) below the baseline temperature of 65 degrees before turning on the heat, and then I use about 0.84 kWh of energy per day for each degree (F) that it gets colder. At the current PEPCO price of 10.96 cents/per kWh, I pay an extra 10 cents per day for each degree colder that the outside temperature goes below about 59 degrees.
On the cooling side, the curve looks like this:
I'm apparently willing to tolerate large excursions before turning on the air conditioner (up to 10 degrees above the 65 degree baseline), and then I use 1.31 kWh of energy per day for each degree above that (for a cost of about 14 cents per day for each degree).
Finally, it's worth noting that I use 9.7 kWh of energy every day, no matter what the outside temperature is, just keeping the house going. I know for a fact that my refrigerator uses about 3.8 kWh every day on average, or about 40% of the total. It's a very old refrigerator from 1982 (!) which needs to be replaced. I used my handy Kill-a-Watt energy meter to measure this and other devices in the house. The refrigerator is by far the largest constant energy user.
Interestingly, last winter I changed from incandescent and halogen lamps to compact fluorescent bulbs. I predict this should save me between 1-2 kWh per day. A change such as this is barely detectable on the graphs, given the season and monthly fluctuations.
As one final exercise, I can estimate the overall efficiency my house, the effective "R-value". This quantity is defined as the reciprocal of the amount of heat lost per unit time per exposed area per degree temperature change, and has units of ft2 per (BTU/hour/Fahrenheit). I already know the second quantity, since it's the linear heating coefficient I found above (0.845 kWh/day/F = 120 BTU/hour/F). The exposed area of my house is about 2000 ft2, giving an effective R-value of 17. (NOTE 14 Jan: my original value of R-0.7 was had a unit conversion error and was incorrect).
An overall insulation efficiency of R-17 is okay but not great. As pointed out here, a house in my region (zone 2) demands an R value in the range of 18 (walls) to 49 (attic). However, as one of my commenters notes, there are other factors to consider, like how much air circulates through the building.
Remember that this data is all based on my house before I made the few changes above. Neither my usage data nor the climate data for the winter heating season are available yet. I hope to see improved efficiency!
Update (14 Jan): Oops! I made a unit error when converting from kWh/day to BTU/hr (missed a factor of 24). After the correction, the overall insulation efficiency of R-17 is more reasonable.
I live in a region which is heating-challenged. Every house or apartment I've lived in has had issues with heating in the winter and cooling in the summer. Builders in this area just don't seem to get that a little insulation goes a long way. For my current house, the homeowner's association also decided in its infinite wisdom that it would rip out all the old oil-fired boilers because they were too expensive, and replace them with electric baseboard heaters, because they are more economical. Whatever insane reasoning that led to that decision is now negated, especially since electricity has doubled in price over the past two years here. While it is true that electric heaters themselves are 100% efficient, the power plant and transmission lines are not. Furthermore, baseboard heaters tend to be mounted on outer walls below windows, so much of the heat can be conducted through the wall and escape the house.
I'm trying a few new strategies to try to make my house more comfortable, given its current limitations. First, I added transparent window films to almost all of the windows. The idea is that they hold an still pocket of air against the window, which adds an extra insulation factor. They also can contain small drafts so that cold air can't get in. It does take some work to install them, which basically involves stretching a huge sheet of saran wrap onto double stick tape mounted on each window frame, but eventually I developed a pretty efficient method (especially for smoothing the wrinkles).
A second thing I did was install curtains in the living room doorways, in order to keep the heat from escaping to colder parts of the house from the room I use most. These are cheap but heavy curtains I got on sale at Wal-Mart, hung from an expandable shower curtain rod across two doorways. Finally, I put some foam-board over my back door. It's a thin wooden door that conducts a lot of heat out.
I think these efforts have helped in a very qualitative sense. The living room is much less drafty, especially near the windows. Before installing the films, a cold down-draft from the windows would collide from an up-draft from the heaters to make chilly turbulent zone right where I was sitting. These drafts are gone now. The curtains also definitely help keep the heat where I appreciate it most.
Comfort is good, but I'd also like to know if this is saving energy and money.
PEPCO kindly puts my energy usage history on each bill, so it was a matter of collecting a few old bills and entering them in the computer. That's shown in black below (click for larger image).
The plot shows the number of kiloWatt-hours I use each month (ignore the red and blue curves for the moment). Unfortunately, I don't have data yet for December, the first month that I installed the window films or curtains, so I have to put the efficiency question on hold for now.
I decided to check out this plot a little more carefully. I use the greatest energy in the winter, obviously for heating. There are also small bumps in the summer, corresponding to cooling. Up until recently, I had a very old air conditioner which I rarely used, so my cooling expenses have never been large.
What to compare this with? Well, the there is a nifty number called a heating degree day used for heating calculations. Basically, any day that the mean temperature dips below 65 degrees Fahrenheit is considered a "heating day," and for that matter when the mean temperature is above 65 it is a "cooling day." The number of heating degree days is the number of degrees the mean temperature is below 65. The US National Climatic Data Center (not to be confused with the Climactic Data Center! Ooo la lah!) provides tabulated historical heating and cooling degree day data. The monthly total heating and cooling degree days are shown in the above plot (red=heating; blue=cooling; averaged over Maryland & Washington DC).
It's no big surprise that the heating and cooling curves match up with my energy usage pretty well. It's physics after all.
In fact, the Mr. Quantitative in me wants to do more. I decided to perform a linear regression between these quantities, with energy usage per day as the dependent variable, and heating/cooling degree days per day as the two independent variables. The simple function I tried was:
E = Constant + H(Th) + C(Tc)
where H(Th) is some function of heating degree days (per day), and C(Tc) is another function of cooling degree days (per day), both of which describe power usage versus temperature. This equation has the interpretation that I use some constant electric power all the time (for lights, water heater, etc.), plus the amount I use for heating and cooling, which depend on temperature.
The obvious choice is to make the two electric heating functions, H and C, proportional to temperature. However, I found that wasn't a good fit, as you will see below. Instead, there is an activation threshold. For small temperature excursions, no heating or cooling is required, and I don't use energy. This would be my comfort zone, the temperature range I'm willing to tolerate. I imagine I have a larger comfort zone than many people. As the outside temperature gets more extreme, then I use energy to maintain the inside house temperature within the comfort range. This function can be written as a constant when the heating/cooling temperature is within the comfort threshold, and a linear function outside of that. The linear coefficient of the function describes the number of kiloWatt-hours per day needed to heat (or cool) the house one extra degree Fahrenheit.
The fit works quite well, and here is how the results look. On the heating side, the function H(T) looks like this:
This means that I am willing to tolerate mean outside temperature drops of about 6.5 degrees (F) below the baseline temperature of 65 degrees before turning on the heat, and then I use about 0.84 kWh of energy per day for each degree (F) that it gets colder. At the current PEPCO price of 10.96 cents/per kWh, I pay an extra 10 cents per day for each degree colder that the outside temperature goes below about 59 degrees.
On the cooling side, the curve looks like this:
I'm apparently willing to tolerate large excursions before turning on the air conditioner (up to 10 degrees above the 65 degree baseline), and then I use 1.31 kWh of energy per day for each degree above that (for a cost of about 14 cents per day for each degree).
Finally, it's worth noting that I use 9.7 kWh of energy every day, no matter what the outside temperature is, just keeping the house going. I know for a fact that my refrigerator uses about 3.8 kWh every day on average, or about 40% of the total. It's a very old refrigerator from 1982 (!) which needs to be replaced. I used my handy Kill-a-Watt energy meter to measure this and other devices in the house. The refrigerator is by far the largest constant energy user.
Interestingly, last winter I changed from incandescent and halogen lamps to compact fluorescent bulbs. I predict this should save me between 1-2 kWh per day. A change such as this is barely detectable on the graphs, given the season and monthly fluctuations.
As one final exercise, I can estimate the overall efficiency my house, the effective "R-value". This quantity is defined as the reciprocal of the amount of heat lost per unit time per exposed area per degree temperature change, and has units of ft2 per (BTU/hour/Fahrenheit). I already know the second quantity, since it's the linear heating coefficient I found above (0.845 kWh/day/F = 120 BTU/hour/F). The exposed area of my house is about 2000 ft2, giving an effective R-value of 17. (NOTE 14 Jan: my original value of R-0.7 was had a unit conversion error and was incorrect).
An overall insulation efficiency of R-17 is okay but not great. As pointed out here, a house in my region (zone 2) demands an R value in the range of 18 (walls) to 49 (attic). However, as one of my commenters notes, there are other factors to consider, like how much air circulates through the building.
Remember that this data is all based on my house before I made the few changes above. Neither my usage data nor the climate data for the winter heating season are available yet. I hope to see improved efficiency!
Update (14 Jan): Oops! I made a unit error when converting from kWh/day to BTU/hr (missed a factor of 24). After the correction, the overall insulation efficiency of R-17 is more reasonable.
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