A Family Adventure

Tyson, Emilie & Isaac

Energy Efficient House

First Year Net Zero

Author Emilie Phillips

Our PV solar panels have been installed for a year. We generated 10.75MWh of electricity. Our utility meter says we sold 7,373kWh of that back to the grid. And we used 6,880kWh from the grid. So net, we used 490kWh less than we produced! Our load is dreadfully mismatched with production. We are shipping 3/4 of our production to the grid and then taking it right back. Some of the mismatch is daily — we are at work when the sun is shining. Some of it is seasonal. The most likely culprit for the seasonal imbalance is the hot tub.

Net meter readings

PV production

To verify how much energy we used, I had to figure out the Itron utility meter display. It’s anything but intuitive. The best resource I found was the Eversource FAQ. But while hunting around the internet, I found the generic Itron installation manual. It says the Itron meters use hall sensors to detect energy usage. According to this report, meters with hall sensors can systematically under-report energy usage. Obviously, whatever the meter says is how we are billed, so we will be billed as net zero. But I wanted to know “are we really net zero?” I did a quick comparison of a couple months of utility bills to data from my Sense monitor. They came out similar. So it looks like my smart reader is reasonably accurate.

Posted Apr 11, 2017

Green web hosting

Author Emilie Phillips

We all need to do our part to prevent global warming. According to this report from 2015:

Datacentre web servers, such as those used by Google and Facebook, to blame for 2% of greenhouse gas emissions – about the same as air travel

As my little step towards improving the planet, I have switched this blog to a 100% renewable powered web host provider.

P.S. let me know if anything broke in the transition.

Posted Mar 19, 2017

Heating Season

Oct 20, 2016
Author Emilie Phillips

October 1st we turned the radiant heat on in the sand high mass collector. There’s a delicate balance between turning it on early enough so the sun is still heating the hot water panels on the roof, but not so early that we overheat the house. The one year I turned the sand on at the end of October, we were cold for the next several months. Since then, I have been turning it on in late September or early October (2015 post). Most years, we have turned the sand back off because it got too warm.

Indoor air and mass temperatures.

Indoor air and mass temperatures.

This year was no exception. The sand warmed all the way up to 86F right before a week of 70F+ weather forecasts. So I turned the sand back off on October 15th. Or so I thought. The house kept getting warmer. I must have been too tired when I thought I turned the sand off. What I actually did was turn the slab radiant heat on too. Guess we will be leaving the windows open for a few days to cool down.

Indoor compared to outdoor temperature

Indoor compared to outdoor temperature

Outside it hasn’t cooled off much, so we don’t particularly need the heat yet. For reference, here is our photovoltaic production for the year. The hot water panels are tilted more towards winter solstice sun angle, so they will be producing more heat later.

Monthly electricity production.

Monthly electricity production.

Posted Oct 20, 2016

Hot water solar panels re-pressurize

May 7, 2016
Author Emilie Phillips

We finally got around to repressurizing our hot water solar panels. The process was pretty simple. This is a continuation of the work started February 20th.

First we picked a rainy cloudy day so we didn’t have to worry about the panels overheating. With our brand new pH strips and refractometer we tested the solar fluid in the system.

Solar fluid 9~10 pH

Solar fluid 9~10 pH

Nominally it is supposed to be between pH 8 and 9. So the fluid hasn’t broken down and become acidic. Tyson’s initial measurement of the propylene glycol concentration was probably wrong. He re-measured it later. The fluid in the system reported ~2F in the refractomer. Looking at the chart on the bucket, 2F should mean freeze protection to -6F, pumpable to -15F, burst protection to -50F. The air temperature only dropped to -13F in February, so it seems likely we didn’t damage the pipes.

Tyson adjusting hoses on the two pump system

Tyson adjusting hoses on the two pump system

For the small volume of fluid we needed to repressurize the system, we used a bucket left over from the original installation. It measured at 10F and pH 8.5. This bucket is probably some of what the plumber used when we first had the pipes freeze.

Final pressure -- 25 PSI

Final pressure — 25 PSI

To pressurize the system, we hooked up the output of the sump pump to our new 1/2 HP pump. First we just cycled the system to get any air out. Oddly, more fluid fit into the system with the solar pump off than on. We think we were pumping into the pressure expansion tank. Then, to pressurize, we closed the outlet. This time, the pressure on the gauge rose steadily until Tyson closed the input valve at 25 PSI.

The instructions I had gotten from RadiantTec said to pressurize the system to 15 PSI, but Tyson and I weren’t sure if that should be 15 PSI at the panels three stories up, or down in the utility room. Presumably the system is pressurized to increase the boiling point. If that’s the case, we would want 15 PSI up at the panels. And Tyson vaguely recollected that the original pressure when we moved into the house was more like 25 PSI.

Before next winter we should consider increasing the propylene glycol concentration.

Posted May 7, 2016

Photovoltaic Solar Panels

Apr 9, 2016
Author Emilie Phillips

Kinder Morgan planned a natural gas pipeline right through my town, Mason NH. I opposed it and decided to put my money where my mouth was. I bought photovoltaic solar panels for the house.

Stack of photovoltaic panels.

Stack of photovoltaic panels.

We had considered PV panels 5 years ago, but the return on investment just wasn’t there. Prices have come down significantly since then. The next question was whether to rent/lease or buy. Since we are planning to keep the house for a while, it made more sense to buy. Also, there is now financing available for PV, so we wouldn’t have to pay a lump sum up front. Our neighbors had a good experience with their installer, Revision Energy. So we went with them.

The process was pretty simple. One guy came out and measured our roof, analyzed the sky line, and looked at our past year of electricity usage. He concluded we could reach net zero if we covered left, right and underneath of the hot water panels. We paid a down payment to reserve a spot on the installation wait list.

Inverter installation in the garage.

Inverter installation in the garage.

Three months later our slot came up — right in the middle of sleet season in March. The indoor work went quickly. They ran electric cables down from the roof through the attic. In the garage, they installed a giant white box containing the inverter and monitoring firmware. It connected to our Ethernet switch and our main circuit breaker box.

Hookups for each PV panel.

Hookups for each PV panel.

Outside the house, after it stopped sleeting, they attached horizontal rails to the roof. The giant PV panels mounted to the rails. The panels are parallel to the roof and spaced above it by a few inches.

While they were there, we also paid Revision Energy to install a mini-split air to air heat pump. Future owners can use it as back up heat for the house. We will be using it as an AC to alleviate our summer humidity problems.

Revision Energy was done at that point, but we still had more hoops to jump through before we could turn the panels on. First we needed the electrical inspection. Next we sent paperwork off to Eversource, our utility. Finally, Eversource replaced our regular meter with a net meter. At last we could start producing power, almost a month after installation started.

28.8 kWh produced so far.

28.8 kWh produced so far.

Our first full day of production: 43kWh.

P.S. Kinder Morgan put the northeast direct pipeline on hold on April 20th, and officially canceled it on May 23rd.

All Photos

Posted Apr 9, 2016

Solar Panel Cold Freeze

Feb 20, 2016
Author Emilie Phillips

Valentines Day weekend the overnight temperatures dipped to -13F. I was mostly worried about how cold it would be skiing. While I was off skiing, Tyson discovered another problem — the pipes to the solar panels froze.

Outside air temperatures for the weekend.

Outside air temperatures for the weekend.

Tyson first noticed water running out of the high temperature dump. He found the solar panels at 224F despite the pump attempting to circulate. He turned off the hot water dump since it is ineffective in the winter heating configuration. All it does it dump electrically heated water out of the domestic hot water tank. Then he turned his attention back to the pump. Presumably the pipes carrying solar fluid through the unheated attic had frozen, or at least congealed enough the pump couldn’t push the fluid up. However, before Tyson could debug more, the pump started circulating water and all the temperatures equilateral. Either the bright sun or the warming air had defrosted the pipes.

224F out, 57F in

224F out, 57F in

The next morning was almost as cold. Tyson headed off to work. I had President’s day off, so I ran up and down the steps every three minutes checking on the solar panels. They started out frozen. I preemptively disabled the hot temperature overflow. While waiting, I inspected the old glycol tub for any clues. It had a sticker converting from refractometer reading to freeze point. Our first winter in the house, the pipes froze once, but the plumber fixed it by adding more anti-freeze. I had no record of the final concentration. Depending on the concentration, the freeze protection might be anywhere from -10F to -100F. Around 9:30AM the fluid finally defrosted enough for the pump to circulate water.

The original anti-freeze. Unknown concentration.

The original anti-freeze. Unknown concentration.

The temperatures seemed reasonable, but the pressure was low — only 12 psi. Tyson remembered the system new holding more like 30 psi. So, I drained the pipes and shut off the pump in case there was a leak.

That evening I called customer support for RadiantSolar. The technician seemed to think it was unlikely the pipes had frozen or burst. He also thought it was unlikely our solar fluid had degraded significantly in 5 years of operation. He suspected our problem was we had neglected yearly maintenance to re-pressurize the system.

We needed a known mix of propylene glycol and water to refill the system and we needed a pump. To get the right mix, we either needed a refractometer or premixed solution. I called around to every hardware store and automotive store looking for a refractometer. Nobody had one in stock. Tyson found a premix available at some of the local Home Depots. Friday evening he raided all the stores in Nashua and came up with 11 gallons and a sump pump rated to 30 feet. The premix rating is: freeze protection to -22F, pumpable to -27F, burst protection to -80F.

Saturday morning we poured 5 or so gallons into a bucket, hooked up the sump pump, and waited for the temperatures on the solar controller to equalize. They didn’t. The sump pump just wasn’t strong enough to push the fluid all the way to the top of our house. So we turned on the standard solar pump in series with the sump pump. The temperatures changed rapidly, and the water level in the bucket dropped. We poured more fluid into the bucket.

Almost done pumping

Almost done pumping

The new fluid was blue whereas the old fluid had been pink. We tested the old pink fluid with a PH test strip from the hot tub. It’s an imprecise measurement, but the fluid didn’t seem excessively acidic. We kept pouring jugs into the bucket. We ran out of jugs, so we moved the sump pump to a smaller bucket to keep it submerged. Finally the fluid level stopped dropping and the fluid changed color from blue to pink. Tyson had bought barely enough anti-freeze to fill the pipes from the solar panel to the utility room. I had not drained the radiant piping in the floor. The rest of the morning, we progressively flushed air from each sub-system connected to the panels.

Then it was time to re-pressurize the system. The sump pump just couldn’t make the pressure budge above 12 psi. Not surprising considering it couldn’t circulate fluid without help from the solar panel pump. We tried elevating the bucket for just a little bit more pressure.

Next steps: buy a stronger pump, a refractometer calibrated for glycol, and PH strips.

Solar panels off

Solar panels off

Solar panels on

Solar panels on

With the panels turned off, the sand and slab temperature dropped significantly despite several sunny days. Since turning them back on, the mass temperatures have bounced back.

Posted Feb 20, 2016

Firewood

Nov 8, 2015
Author Emilie Phillips

Come fall, I realize that I am almost out of time for all the chores I planned for the summer. Collecting firewood is one of the most critical ones. We finished this weekend.

Hollow oak tree

Hollow oak tree

Last year we had troubles filling our wood rack in the fall, and the winter was extra cold and cloudy which left us scrambling at the end of winter. This year, Tyson wanted to make sure we had enough. In the spring he cut down some half dead trees on the property. Some of that wood was dry and split easily. Other sections were green and would not split even after drying all summer. We even chopped up some of the planks from the old deck, but we do not know how well they will burn.

Isaac helped just a little

Isaac helped just a little

I helped Tyson find more standing dead wood on our property. But that was not enough. He cut down some more of the half dead trees. The bottom of the big oak turned out to be completely hollow. Unfortunately, the dead parts of the oak were filled with carpenter ants, so we can’t bring them into the wood room. By this point, if we could get the green wood from the spring to split, we probably had enough wood for the winter. But Tyson wanted to be really sure. So he scavenged on the airport property and found a large aged blow down and several trees chopped down by a beaver. We also borrowed the neighbor’s hydraulic splitter to split all the wood, even the brand new green wood.

Wood room

Wood room

Next year's wood

Next year’s wood

This weekend we split and split and stacked and stacked. I stacked the wood up to the rafters in the woodshed. With all the new dried wood Tyson found this weekend, we have more than enough dry wood for the winter. The outside wood rack is piled to the tippity top with plenty of green wood for next year and all the extra dry wood. I think we are probably set for the next two years especially since this winter is starting warmer than average.

Indoor and outdoor temperatures

Indoor and outdoor temperatures the last 30 days

Posted Nov 8, 2015

Turned the Sand On

Sep 28, 2015
Author Emilie Phillips

We started preheating the house. We had unseasonably late warm temperatures, so I hadn’t been thinking about. Then all the sudden on Sunday morning, the 27th, there was frost on everything. So, Monday morning, we switched the valves to start heating the sand from the solar panels. We are still heating the hot water tank too. The above image shows temperatures before and after turning on the sand.

Since we have been in the house for a few years, I analyzed previous years to see if it mattered when we started heating the sand from the solar panels. Results are highly inconclusive. These plots show the average sand temperature the first week of November and December as a function of the day we turned on the sand. Last year we turned the sand on first on September 22, but not long after we turned it off again because the house was too hot. We turned it on for good October 8th, 2014. I plotted the data both for the first day we turned the sand on, and the second time.

Temperatures relative to first time we turned on the sand.

Temperatures relative to first time we turned on the sand.

Sand temperatures relative to last time we turned on the sand.

Sand temperatures relative to last time we turned on the sand.

And for my own reference, the dates we turned the sand on were

  • 2011: October 3
  • 2012: October 8
  • 2013: October 21
  • 2014: September 22, October 8
  • 2015: September 28

Posted Sep 28, 2015