Our $2K solar space and water heating system provides solar water heating and also space heating to part of our house. Until recently the backup heat for this part of the house was a propane forced air furnace that came with the house. But, last winter the furnace died and the replacement cost was $6000. So, instead of replacing the furnace, we added a backup heat system that just adds heat to the large solar heat storage tank when there is not enough sun to keep the solar tank warm. This approach cost about $300 (pretty good saving), and has the advantage that we no longer have a noisy and potentially unsafe gas furnace hung from the floor just below our bed.
The new backup heat system is pretty simple. Its just an electric hot water heater that sits next to the solar tank with a small pump to circulate hot water from the electric tank to the solar tank when the solar tank temperature drops below a setpoint. The heat is distributed to the room above by the same radiant floor pex tube system as before.
The backup heat source electric hot water tank
The TopsFlo pump that circulates water between the backup tank and the solar tank is at the bottom of the picture — only 15 watts.
Diagram of the new backup heat system — really simple.
Solar air heating collectors provide a nice stream of heated air during the day when the sun is shining on them, but at night, the flow often reverses and brings unwanted cold air from the collector into the room.
Backdraft dampers are added to prevent this reverse flow of cold air. There are several types of dampers — both DIY and commercial.
I’ve added a section that lists the ones I know about — if you know of others, please let me know.
With this spaghetti squash and meatballs recipe, you can reduce the carbohydrates and increase the vegetable servings by skipping pasta and serving the Italian-seasoned turkey meatballs and quick, homemade marinara sauce over thin strands of cooked spaghetti squash instead. Cooking the squash first in the microwave and then in a skillet to cook off the extra moisture, gives the squash a more spaghetti-like texture.
In this healthy main-course chicken salad recipe, dandelion greens and curly chicory pair marvelously with a wildly flavorful mushroom-sesame dressing, roasted chicken thighs and succulent roasted squash. Toss the salad with the dressing just before serving so the greens don’t get too wilted.
When Bruce looked at where his electricity was going, he found that about a quarter of his total electricity use was to run his pool pump. He decided to install a new pump that would be run from PV modules.
Bruce’s report gives details on the design and installation of the new pump, and on how the economics is working out. The drop in PV module prices in the 6 years since the system was installed, the payback period would now be substantially shorter.
Two 170 watt PV panels in series drive the DC motor pool pump
The installation is simple consisting of only the two 170 watt PV panels (above), a controller, and the DC powered pool pump itself. Given the efficiency of DC pumps and the minimal losses its a very efficient setup.
The new pool pump — the controller is visible on the wall behind the pump
An alternative to Bruce’s approach would be to retain the existing AC pool pump and add a grid-tie PV system for the whole house that would power both the pool and the rest of the house loads. This is appealing in that one system does both jobs, but the low efficiency of typical AC pool pumps appears to require a much larger PV array (perhaps a 3000 watt PV array just to drive a 1.5 hp AC pool pump 8 hours a day). So, the dedicated PV array to drive the DC pool pump appears to be the more cost effective solution — do you agree?
Two speed AC pool pumps run for longer periods at lower speeds also appear to offer a larger saving in electricity at a modest initial cost.