EV Makers: Here my tiny voice

I am proud to say I have not owned a car since 1989 (and technically I think my parents owned that one). Yes, I have the benefit of living in Manhattan for the past 17 years and have had a walking commute for most of that. However, we do often travel outside the city esp. now with our upstate place. Zipcar and rentals have filled that need. However, they are either convenient and overpriced (Zipcar, Manhattan rentals) or inconvenient and cost effective (suburban rentals). In addition, fossil fuels are not everlasting and pollute. I have spare solar energy and I want an electric car.

Car industry (traditional and upstarts) I'd like to list my EV wants so that at least some of this trickles into gen 2 (the first I'll consider buying):

- 150 miles of range on a full charge (my infrequent but typical trips are 100 miles)

- 50% recharge time in 5 mins; 80% recharge time in 15 mins; and 100% in 30 mins

- Swappable batteries and a network of swap and charge stations (at least on major highways)

- Four door hatchback in roughly cross-over size (I don't really care that much about looks...with technology its always function over form)

- Solar panels on the roof and wherever else you can put them for battery refill; I've also heard of small wind generators that might apply...look into that

- Home charging stations that don't cost over $1,000 including installation and are based on a standard so it outlives the life of the car

- Under $30k all in

That's about it. We're not that far off right now. Get on it.

Net Zero for 2010 by 73kwh

We made it. We were net positive on our energy use for 2010 by a tiny 73kwh. That's 1.25% (73/5799 kwh used). I guess my engineering work on sizing the solar relative to the geo and general usage was pretty accurate. But maybe it wasn't.

The tweak I made back in Nov raising the geo output temp for the radiant from ~95 degrees to ~105 degrees has initiated big savings. Last winter, we had days when it was cold where the geo ran almost the whole day (both in residence and away). It wasn't because it was struggling to keep up as much as the temp of the water feeding the radiant wasn't high enough to warm the house to the target temp. Thus, the geo kept running as the thermostats were never satisfied. The 95 degrees in the floor was not making our main zone 70 when it was under 20 degrees outside (and wasn't keeping up with 53 when it was below 10 degrees when we were away).

Raising the output temp by 10 degrees raises runtime energy use but only about 10-20% from what I can see. However, its had a dramatic effect on total runtime. The geo can now hit the interior temp even when its below zero (as it was a few days ago) and doesn't run nearly as much. Early signs point to about a 40% energy savings during this Jan compared to last. Projecting that out over the year we'll have upwards of 600-800kwh to spare this year. Looks like just the right amount to power an electric car ;)

Heading Toward Zero

Coming to the last few days of 2010 spending it at the house. Looks like we'll be right at net zero for calendar 2010. December has been colder than average with few days above freezing but a good deal of sun for solar gain. Ambient away energy use was around 20-25kwh/day as we keep the place at 53 when not here. That is on target for my rough formula of 1kwh per HDD.

Since we've been here, we've been using about 65kwh/day of which about 45 is geo heating. We keep it at 69 (I'd be fine with 66-68 but others have differing opinions). That still maintains the 1kwh per HDD. As usual, we've been using the fireplace at night which generally carries the heating load until midnight. Overnight, the geo's runs have been interesting. Its cycling on for 10-15 mins and then off for 5-10 mins and stretches those off cycles out as it gets further into the night. Meaning that, even though the temp is dropping, its mostly bringing the slab up to temp which heats into the morning. Since I turned the geo target temp up to 105 its performed much better at getting to and maintaining 70 when we need it. I haven't actually noticed much more energy usage vs. when it was lower last winter. So our cycles are longer and less frequent when it needs to heat the slab from relative cold (when we're not here and maintaining 53) and shorter and more frequent when keeping the slab up to temp at 70. I also insulated several of the radiant pipes in the mechanical room which is now not as hot and thus transferring that energy into the slab.

One interesting observation was that I thought we were saving a couple of cycles and thus energy by using the fireplace at night. That might not be linear savings. The reason is that the geo doesn't end up running for 6-8 hours at night and the concrete slab gets cool (except around the fireplace). When the temp does drop after midnight, the geo has to cycle longer and more frequently to pick up the slab temp. One night I didn't use the fireplace. When I checked energy use for geo in the morning, I found it was about 20% lower than each of the previous few nights where the temp was consistent around 20 degrees outside. Checking the run pattern, it cycled on notably less and that could only be due to it only having to maintain the slab temp vs. a pickup due to the fireplace keeping it off. Thus, geo and radiant do work if you let them. Now I'm wondering if I should only use the fireplace when we need quick pickup. Doubtful since the aesthetic and entertainment value is still so high.

Heat through the fall

I've been happy that we didn't need heat but for two days we were in residence at the house during Oct. I think I've zeroed in on the right ambiant temp, 53 degrees, for when we're not there. In fact, during Nov, the heat has only run 2 or 3 days and in single, light 2-3 hr cycle on those days. Overall, I know this will be significant kwh savings during this mid-Oct to mid-Dec utility billing cycle. Last year, we used 1,000 kwh during this period. To date for this period, we're actually net-positive by 100 or so kwh. That'll quickly go away this week but we certainly won't use 1,000 by mid-Dec. I'm guessing we'll be more in the 400-500kwh range. That'll leave us with about 1,000 kwh credit with the utility from summer generation. Even though we'll be up for the holidays through the end of the year, that should easily be enough to be net positive for the year. I'm guessing we'll have 300-500kwh left over depending on how meak Dec solar generation is (yes, we can sneak out 200kwh generation in Dec).

Now that we're up here for Thanksgiving week, I'm focused on learning and optimizing for in-house use. Yes, we're sized for and able to achieve net zero partially because we're only here about 25% of the time. While that does use less heat overall, its not 25%. The most expensive heating cycle is heating from 53 to 70 when we're coming up. I've made this better by only heating the bedrooms at first and using the fireplace for pick-up but it still generally uses 50kwh to warm the place when the outdoor is 35-40 degrees. Once the house is warm, it generally only cycles overnight in this temp range and thus only uses 12-16kwh per day. Our non-heat usage is generally 15-20kwh. At least one principle of Passive House design is true of solar gain and ambiant heating sources keeping the place warm during the day.

I've been using the fireplace at night and there is a benefit of saving probably one cycle from that heat (5kwh or so). However, the downside is that it allows the radiant slab to get cool and thus the geo has to work harder when it does cycle on. I'm guessing there's only a small net and, if we didn't enjoy the fire so much, I probably would forgo most nights.

The net is, being here full time doesn't increase energy usage for heat as much as one might think. I'm guessing it is double but not 200% as per our usage of the house would indicate. We'll sanity check those numbers after this week.

Weekend Heat Experiment

This weekend was the first opportunity (cold enough to warrant heat) to experiment with some strategies to pickup the heat in the house from cold with the least amount of energy used. Fortunately, our geo system was fixed on Friday so we had all resources available. The plan was to turn the geo on and to use the fireplace at the same time for quick pickup. When we got to the house, the indoor temp was 57 and outdoor was in the mid-40s (declining to upper 30s overnight). The geo was started around 4pm and I started the fire around 5pm. I kept the fire at a decent mid burn. We got pick-up of about 4 degrees an hour in the main room (about 35x20 and 12-16 ft ceiling) primarily from the fire. Thus, by 8pm we were in the upper 60s and comfortable.

By that time the geo had the slab warming up (it takes 2-4 hours to heat the concrete slab to noticeably warm from cold). It then heated the bedrooms since the draft warmth from the main room into the bedrooms is only minimal. Those were in the upper 60s by bed time and the fireplace warmth lasted most of the night.

However, the geo did run more then I would have expected overnight. There was one anomaly affecting this as one electronic valve controlling radiant to the basement floor appears to be malfunctioning and always open thus diverting hot water there. However, this longer run most likely due to the main room slab (which is huge) still needing to warm up as the fire pushed the thermostat to stop calling for heat early in the evening. One thing I'll do next time is to not turn the geo on for the main room but just for the bedrooms while I'm heating up with the fire. The main room draws most of the hot water from the geo and thus is not heating the bedrooms optimally. Focusing the heat in the bedrooms will pick them up quickly while the fire warms the main room. I want to see this effect as the one downside is that the main room slab will remain cold (other then right around the fire) and at some point in the night will have to be heated which will be a long cycle. That's inevitable so I'm hoping that the run is only 2-4 hours to warm the slab and pick up the one degree. Geo is much better at maintaining temp then raising it rapidly.

We used about 100kwh total from Friday 4pm-Sunday 2pm. From historical usage, we know that about 30-40kwh was due to non-heating items (cooking, DHW, washing machine, etc.). Thus, 60kwh was for heating. Too high for this temp and time of year. Hoping to keep that around 30kwh.

Summer "Netting"

This summer we netted 2,440kwh of electricity to carry us through the winter heating season. This was 740 hours more than last summer. This was partially due to higher generation this summer (about 220kwh) as July in particular was a banner month vs. a rain filled summer '09. However, the additional 520kwh was purely from conservation.

First, we still had some trailing construction work last summer so usage was higher due to that but it was minimal. It has mostly come from learning about our usage patterns in no small measure from our TED whole house monitoring system. That's really provided deep insight into what appliances use what amount of energy. We've done things like only use one hot water heater in the summer (and probably will continue to into winter except when we have overnight guests) and using our oven more intelligently (cooking items at the same time or consecutively to leverage the previous cooking heat already in the oven).

And so far this fall we haven't had to use the geo heat (and good thing since that's still being repaired). The temps have been warm, we've been getting good passive solar gain, and the fireplace has supplied a nice pick-up for cooler nights. I'm hoping not to have to use regular geo heat until mid-Nov on our way to a net zero year.

Question about Passive Houses during Transitional Months

One thing that's notable about super tight, super efficient houses is that how you live in them or "lifestyle" is different (at least to me as I think about these kinds of things). I'm not talking about lifestyle changes like "sorry honey, you have to put on the sweater and wool socks as we're keepin' in at 62 in Dec" or "we'll be 'shower optional' on Thursdays". Its how you experience the house leveraging the external environment to dictate the internal one.

One of the incorrect early approaches to super tight houses was to limit glazing, air flow, and any other way the exterior environment would affect inside. Newer houses like ours not only embrace the external environment, we're somewhat dependent on them to function efficiently. The simplest example of this is in passive solar gain where you're using the lower sun in fall/winter/spring to give you a heat gain. However, there are more subtle ones like having east and west ventilation (where winds tend to blow at most times) for summer cooling. It also brings the outdoors in which is the biggest reason to have a house out in the woods.

This weekend, we had gorgeous weather upstate including Sunday night getting down to 46 degrees. We had the house wide open all day when it was 80 out (house was a comfy 75). Once the sun went down, the temp dropped quickly as there was no humidity. We immediately closed up most doors and windows to preserve our natural heat and that it did.

However, this prompted a question in my mind about Passive Houses. When you're in the transitional fall/spring seasons where sunny daytime temps are in the 60/70s and you want to open some doors and windows to enjoy it, are you restricted from doing that in a passive house given there can't be that level of heat loss at night (say if it drops into the 30/40s)? The house will perform if you keep it closed up but is that the lifestyle in a Passive House? Are you so dependent on heat gain during the day that you can't risk having natural ventilation in the transitional months? Anyone out there with a take on this?

That said, even our house is tricky during the transitional months. In the scenario described above, we'd probably have a few windows and doors open during the day and get nice solar gain on our concrete slab. We'd close them as the sun went down. Most likely the house would stay warm passively but in the case of a strong drop or that we forgot to close something early enough, we have the geo system there to warm us up.

Admittedly, this is a scenario where radiant is not at its best. Periodic and quick warm-ups aren't great with radiant. It takes 1-2 hours just to get the slab up to temp. When that happens for a couple of hours and then turns off for several hours the slab cools. Then it has to warm it all again. I experimented with turning the thermostat down in this scenario which made it run less but some in the household were cool at times. This year, I plan on making liberal use of the fireplace (cut up about a cord this weekend!) and will even try electric space heaters that can warm a 500 sq ft area quickly.

Passing 10Mwh

I'm not that into arbitrary milestones but figured it was of note passing 10Mwh of solar generation this Labor Day weekend. We're about 19 months into our install. Performance has been notably above the estimate provided by the installer (I think he sandbagged so he didn't get calls asking why it was low) and 10-15% below optimal for the area (it's well below optimal for the latitude but that's pretty irrelevant as it doesn't take weather into account).

That 10-15% down was expected based on the solar pathfinder the installer did. We have one big oak that we wanted to save to the west of the house and from Sept through March it gives partial shade for about 60-90 mins each afternoon. Production Oct through mid-Feb was also below expectations as the low sun clipped some of the surrounding trees. I've been doing some thinning of the evergreen hemlocks to the south and west so we'll see how that helps. Fortunately, this summer was hot and dry so Apr-Jul met or slightly exceeded optimal (with July providing a new high point at almost 800kwh).

I have about 1100kwh banked with our utility. My estimate is I need about 1700 to be net zero for the year. Its a Sept+Oct race as Nov will start us back to being net positive for the month. I think my new heating strategy will both allow me to bank more in Oct and use less which I imagine will be the difference.