Happy Winter Solstice!
It seems like it was summer just yesterday but it is definitely winter now.
Susan has invented a new field of "tree engineering". In order to make our Christmas trees fuller and more symmetrical, she has pioneered techniques such as "branch insertion". (Required tools: electric drill and sharp knife.) Her latest development is "tree weaving". I was skeptical at first of the idea of combining 2 sparse trees but the result was an undisputable success.
When we started to design the house, we knew we wanted to use solar energy but we weren't sure if we wanted solar thermal, solar electric, or both.
By the time we started building, we had decided to install solar thermal since it would have the biggest impact on our energy usage. Solar electric technology and incentives were also in flux and it seemed like a good idea to wait and see how things changed.
After the house was built, the electricity usage was higher than I expected. We spent quite a lot of time trying to understand where the electricity went and then trying to reduce it. We had some big successes like reconfiguring the hot water recirculation system but in spite of this effort, we realized that it was time to consider a solar electric system.
The New Solar Electric System
Over summer, some friends visited and brought 4 proposals they had received for putting solar electric panels on their house. I was quite surprised at the efficiency, net cost, and short payback period for the systems in spite of our friend's house being less than ideally situated for solar power. Encouraged by this, I called 2 contractors: the one who put in our solar thermal system and the contractor our friends chose.
It was clear I had a lot to learn when I saw proposals that claimed to reduce our electric bill to zero in spite of being too small to cover 100% of our electricity usage. It turns out that this is due to 2 factors.
First, in the summer the system will generate more electricity than we need and the excess will be "sold" back to the utility for a credit. During the winter, we will "spend" this credit to buy electricity since the system won't be generating enough to cover our needs. Once a year we will pay for our net usage, if there is any. (This fall, California passed a law that says the utility has to actually pay for any balance in our favor instead of just keeping it for free which is what they get to do now.)
Second, most people pay for electricity based only on how much they use and not when they use it. With solar electric systems, most people switch to a time-of-use rate plan. This means that any excess electricity generated by the system during the day is "sold" back to the utility at peak rates. If you can time shift electricity usage to non-peak (night) hours, you can buy electricity back at a much lower rate. For example, if you switch 1 kilowatt/hour of power from peak to non-peak hours, you will get a credit for the difference in price between the peak and non-peak costs for the kilowatt/hour.
From the energy conservation point of view, we are helping he utility by lowering the amount of electricity they have to generate at peak times. It is this quantity that determines how much generating capacity they have to build. The electricity we use at night is most likely excess capacity.
For example, we put a timer on our well pump so that refilling the water tanks happens at night. The pool cleaner now runs at night instead of during the day. Our last electric statement showed that we had a net usage of $25. (This was also November when the sun is close to winter solstice.)
One big surprise was that the quantity of electricity generated is effected much more by the length of the day than the angle of sun. I had expected the peak output of the system to drop dramatically as the winter solstice approaches. What is happening is that the output at noon is still quite high but the overall output is less due to fewer hours of sunlight.
At the time we put the solar thermal system in, there were very few real time monitoring tools available. Fortunately, solar electric monitoring systems are much more advanced. Our system is connected to the internet and it frequently uploads performance data to a monitoring company. They have a web site where I can go and see both instantaneous or historical performance. It is a public site so the data is visible to everyone:
Click to open our solar monitor web site
Furniture
I finished another bed for the house recently. It was a design I've been thinking about for years but didn't have the space or equipment to handle: both the headboard and footboard are made of one continuous curve. There are several ways of bending wood: heating with steam, soaking in chemicals, or laminating thin strips. The first 2 require specialized equipment that would be prohibitive for a project of this size. The last approach is not only easier, it is much more interesting from an engineering point of view.
In order to bend by using laminations, you need a form to bend against. You also need to cut your wood into strips thin enough to bend around the form. In the case of the bed, I ended up with 19 strips each 3/32" thick and 12' long. These are glued together and clamped to the form. When the glue dries, you end up with a completely rigid, very, very strong piece of wood bent to the shape of the form. This sounds pretty simple but the glue up is nerve racking; the glue dries in 15 minutes at 70F so it has to be spread on all 19 laminations, then combined and clamped to the form in a very short time. I cheated a little by doing the glue-up early one cool morning; the cooler it is, the more time before the glue sets.
This is the 2nd of 3 beds I need to make for the house. Adam and Holly have also requested beds. Fortunately, each one is different with different challenges.
Winter Morning
Susan has invented a new field of "tree engineering". In order to make our Christmas trees fuller and more symmetrical, she has pioneered techniques such as "branch insertion". (Required tools: electric drill and sharp knife.) Her latest development is "tree weaving". I was skeptical at first of the idea of combining 2 sparse trees but the result was an undisputable success.
Two trees woven together
When we started to design the house, we knew we wanted to use solar energy but we weren't sure if we wanted solar thermal, solar electric, or both.
By the time we started building, we had decided to install solar thermal since it would have the biggest impact on our energy usage. Solar electric technology and incentives were also in flux and it seemed like a good idea to wait and see how things changed.
After the house was built, the electricity usage was higher than I expected. We spent quite a lot of time trying to understand where the electricity went and then trying to reduce it. We had some big successes like reconfiguring the hot water recirculation system but in spite of this effort, we realized that it was time to consider a solar electric system.
The New Solar Electric System
Over summer, some friends visited and brought 4 proposals they had received for putting solar electric panels on their house. I was quite surprised at the efficiency, net cost, and short payback period for the systems in spite of our friend's house being less than ideally situated for solar power. Encouraged by this, I called 2 contractors: the one who put in our solar thermal system and the contractor our friends chose.
It was clear I had a lot to learn when I saw proposals that claimed to reduce our electric bill to zero in spite of being too small to cover 100% of our electricity usage. It turns out that this is due to 2 factors.
Solar Penels (in the middle, left of the solar thermal panels)
Solar Electric Control Panel
First, in the summer the system will generate more electricity than we need and the excess will be "sold" back to the utility for a credit. During the winter, we will "spend" this credit to buy electricity since the system won't be generating enough to cover our needs. Once a year we will pay for our net usage, if there is any. (This fall, California passed a law that says the utility has to actually pay for any balance in our favor instead of just keeping it for free which is what they get to do now.)
Second, most people pay for electricity based only on how much they use and not when they use it. With solar electric systems, most people switch to a time-of-use rate plan. This means that any excess electricity generated by the system during the day is "sold" back to the utility at peak rates. If you can time shift electricity usage to non-peak (night) hours, you can buy electricity back at a much lower rate. For example, if you switch 1 kilowatt/hour of power from peak to non-peak hours, you will get a credit for the difference in price between the peak and non-peak costs for the kilowatt/hour.
From the energy conservation point of view, we are helping he utility by lowering the amount of electricity they have to generate at peak times. It is this quantity that determines how much generating capacity they have to build. The electricity we use at night is most likely excess capacity.
For example, we put a timer on our well pump so that refilling the water tanks happens at night. The pool cleaner now runs at night instead of during the day. Our last electric statement showed that we had a net usage of $25. (This was also November when the sun is close to winter solstice.)
One big surprise was that the quantity of electricity generated is effected much more by the length of the day than the angle of sun. I had expected the peak output of the system to drop dramatically as the winter solstice approaches. What is happening is that the output at noon is still quite high but the overall output is less due to fewer hours of sunlight.
At the time we put the solar thermal system in, there were very few real time monitoring tools available. Fortunately, solar electric monitoring systems are much more advanced. Our system is connected to the internet and it frequently uploads performance data to a monitoring company. They have a web site where I can go and see both instantaneous or historical performance. It is a public site so the data is visible to everyone:
Click to open our solar monitor web site
Solar Information Web Site
Furniture
I finished another bed for the house recently. It was a design I've been thinking about for years but didn't have the space or equipment to handle: both the headboard and footboard are made of one continuous curve. There are several ways of bending wood: heating with steam, soaking in chemicals, or laminating thin strips. The first 2 require specialized equipment that would be prohibitive for a project of this size. The last approach is not only easier, it is much more interesting from an engineering point of view.
In order to bend by using laminations, you need a form to bend against. You also need to cut your wood into strips thin enough to bend around the form. In the case of the bed, I ended up with 19 strips each 3/32" thick and 12' long. These are glued together and clamped to the form. When the glue dries, you end up with a completely rigid, very, very strong piece of wood bent to the shape of the form. This sounds pretty simple but the glue up is nerve racking; the glue dries in 15 minutes at 70F so it has to be spread on all 19 laminations, then combined and clamped to the form in a very short time. I cheated a little by doing the glue-up early one cool morning; the cooler it is, the more time before the glue sets.
New Bed
Bent Laminations
Glueing the strips around the form
This is the 2nd of 3 beds I need to make for the house. Adam and Holly have also requested beds. Fortunately, each one is different with different challenges.
posted by Jim Barstow at
9:22 AM
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