Saturday, October 16, 2010

Time Keeps on Slippin' Into the Future

At our weekly meeting with Paul and Christine this week, we were looking forward to reviewing solar, HRV installation, and insulation bids, and seeing a schedule that would hopefully get us into the house by Christmas. Paul had a schedule, it would not have had us in the house by Christmas in any case, but it really doesn't matter now because the meeting uncovered some problems with the planning that need to be corrected. And that means...yet more delay.

Christine presented the bids from the three solar companies that she has spent the last month collecting for us. If you recall from this post, one of the companies was a roofer who was "looking to get into the solar business". It turns out another was a nonprofit. According to their Web site, they send volunteers up on the roof to install your solar. The bid from this company was the cheapest, and was recommended by Christine and Forrest, our architect. Considering we have about a 45 degree roof, and a previous professional roofer fell from the roof and broke his collarbone, there is no way I am going to let random people clamber around on my roof. I wasn't all that interested in the roofer either. Somebody else can pay for his training. I'm interested in trained professionals who do the job right, and don't punch holes in my roof, and I am willing to pay for that.

In email to Forrest and the previous project manager in July, I asked for SunPower 315 watt panels, the they spec-ed out 225 watt panels. I asked for a maximum power point (MPP) tracking inverter, they spec-ed out a traditional centralized inverter. Only one of the bids came close to matching my specs, and that was the professional solar installation company. I had thought Forrest and Christine were communicating about what I wanted, but, apparently not. I sent Christine and Paul an email detailing *exactly* what I wanted, duplicating my mail of July, and even giving them the telephone numbers of installers and manufactures of MPP systems to call. Christine said she would start the bid process over.

Why am I being so picky about the solar? The main reason is because I want to be able to match the anticipated demand without having to plaster my entire roof with solar panels. With the Sunpower 315's and the MPP system, I can get by with around 20 panels, 2 more than I currently have. With 225 watt panels and a centralized inverter system,  I would need 32.  That would mean that I would need to put the panels on the east side of the roof, which would not get any  sun in the afternoon. Since the highest PG&E solar tariff is in during summer afternoons, keeping the panels on the west side of the roof - where my panels are now - means they will earn the highest return,  in addition to offseting the electricity use.

The difference between the power output from the two types of panels partially explains how I can approximately double the amount of energy I get now out of only 2 more panels than I have now (we now have 18 panels, 165 watts per panel). The other factor is the MPP tracking system. There are now two kinds of power maximizing technology for solar that has come available in the last couple years: microinverters and MPP tracking. Microinverters convert DC to AC directly at the panel rather than at a centralized inverter. The advantages of microinverters are that you don't need any high voltage DC wiring, which is tricky to install,  and you don't need to string the panels like series Christmas tree lights. With series Christmas tree lights, if one goes out, the whole string goes out. Similarly, with solar panel strings  and traditional centralized inverters, if one panel gets shade or clouded, the entire string stops contributing power. With microinverters, the wiring on the roof is AC and the panels just contribute whatever they can without any hindrance from the others.

There are however two problems with microinverters. One is that the most popular, Enphase, uses electrolytic capacitors, just like centralized inverters, that dry out. So they  have a lifetime of around 15 years instead of the 25 years that panels have. There are microinverters around now that use film capacitors and have 25 year guarantees, but they are very new and may be hard to get.  A more serious problem is that the available microinverters won't handle 315 watt panels. The maximum is  275 watts.  Because the microinverters are installed directly on the panel, they must match the power the panel puts out.

MPP trackers, on the other hand, work differently. The inverter is still centralized, but a small module on the panels performs DC to DC conversion to present an optimal electrical load to the solar panel, and a suitable voltage from the panel to match the load. The result is that the power output from the panel is maximized. MPP trackers require high voltage DC wiring and a centralized inverter that communicates with the MPP modules on the panels. But they are not limited by panel power output. There are two companies making MPP tracking inverters that would  handle the 6+ kilowatt array I need, Tigo Energy and Solar Edge. Tigo's will handle the full 6.3 kilowatts,  Solar Edge's will only handle 6.2 kilowatts, but I think I could probably get by with that.

In addition to the solar, we discovered that for the upgrade to 200 amp electrical service, we will need to dig up the electrical conduit that connects our house to mains power and replace it.  I had asked Forrest twice about this in spring when we were in the planning stage, and  the previous project manager (he whose name shall not be mentioned) at least once. Both times I was assured that the conduit was large enough for a 200 amp cable. Paul checked last week, it isn't. So now we have to schedule PG&E to come in and replace it. Being a large bureaucracy, PG&E is likely to take its time, meaning more delay.

Finally, the HRV system design needs a bit of work. If you recall, Forrest had been pushing to extend the mechanical closet on the second floor into the space over the upstairs bathroom door. I was resisting,  hoping we could put it in the downstairs mechanical closet along with the electric on demand hot water heater. It turns out that the hot water heater must go above the solar tank, so it must go in the space above the upstairs bathroom door, but there is no need to make that space an extension  of the mechanical closet. Unlike gas hot water heaters, the electrical kind can go anywhere, just like a dryer, because they don't need venting or combustion air. So I asked Paul to convert that space  into another closet as part of the living space so we can use it for storage.

The HRV ended up in the chase next to the east upstairs bedroom because it was impossible to run the ducting from the space over the upstairs bathroom door or the downstairs mechanical closet to the places we needed it. Our house has two of these dead spaces, one over the kitchen and one over the master bedroom and next to the east upstairs bedroom. With the HRV there, the venting can run below the roof to the living room, east upstairs bedroom, and downstairs master bath,  and through a new ducting soffet to the hallway, thereby covering the entire east side of the house (the west side is served from another HRV in the attic). The problem is there are two existing pieces of ducting in that space: an inactive duct for the former forced air heating system and an active duct that vents the downstairs master bath, which runs through the entire chase, from the master bath to the outside south wall.

The inactive forced air duct is easy enough to remove,  but the active vent for the bathroom is another story. I have been asking Forrest and Paul about this and also Mr. Former Project Manager before he disappeared. Forrest and Paul had some vague plan about rerouting the venting, but last week I found a great Web site about a house in Marin that was remodelled into a passive house (uses no active heating). On that site, they mentioned that they doubled up the HRV and bathroom ventilation. I asked  Paul about this, and he said he would check into it, but we don't know if it is  possible to boost the Fantek  HRV systems up enough to perform bathroom ventilation.

So it is back to the drawing board  for Paul to do  another schedule, and it looks like we will not be back into the house until late January, if then. The solar will probably be the long pole in the schedule.

1 comment:

  1. I'm feeling bad for you with the delays. Still, it will be good to know it's done right when it's over.