If you haven’t heard yet, we are having a party this Thursday evening to announce some new homes we plan to build. If you are coming, you probably like modern architecture, affordable homes, sustainable design or some combination of these three. No matter which is your fancy, we think you have great taste and want to reward you for coming to our party and helping us drink both kegs our friends from Memphis Taproom are bringing with them.

We came up with offering a free 2.0kW solar PV upgrade from EOS Energy Solutions. That’s a pretty small array, but our homes aren’t too large either and they’re pretty high on energy efficient ingredients. Some people smarter than us have calculated that this small array is all it could take to make one of our Postgreen Homes “Net Zero Energy” as long as you are not abusing the outlets too much. Net Zero Energy basically means you are selling as much energy over the course of the year to PECO as you are using from them. Depending on rates, you will often be paid more by PECO than you pay them, for a negative annual utility bill. In a few years when the rate caps expire, it will be even more ludicrous.

This is a big deal. Get excited. We are.

To qualify, you need to come to the party, choose and reserve your house. You will have a week or so to make your final decision on actually putting your money where your mouth is, so don’t feel pressured. If you ultimately move forward, EOS will assist you along with us, in obtaining the proper federal and state rebates that make this PV array possible. We at Postgreen will kick in the remaining balance as part of this one time promotion.

We have one project of three units that will qualify for this promotion only. These are the next three homes we plan to build and we are calling it the Skinny Project. You will have to find out why at the party. So, put this offer in your head when considering what to do tomorrow night (or most likely tonight when you read this). You could sit home and watch reruns of Greys Anatomy or you could come drink our free beer, eat our delicious apps, listen to some sweet music, talk to interesting people and take us up on our offer to eliminate your energy bills forever (or at least the next 30 years or so).

Disclaimer: I am aware that solarization is used incorrectly in the title of this post, but I use it in an attempt to make a joke that is both juvenile and trite. Forgive me.

We are planning on attending a solar happy hour this evening, and that got me thinking about that most recognizable of green features, the solar photovoltaic (PV) panel. Sparkling atop roofs and drinking the sun to power our blenders and televisions, these conspicuous badges of sustainability symbolize a great hope for our energy drunk society. They hint at a power source that might save us from the dreaded consequences of our wanton fuel gobbling. We might, with their help, be able to plunge forward undeterred on our path of mega-consumption. Recycled Big Gulp container in one hand and the wheel of our electric Hummer in the other, we can speed forever down the highway of prosperity (or at least until that Big Gulp makes us stop at a waterless urinal).

Unfortunately, we are still a long way from this dream of boundless solar energy. The resource is there, a churning ball of nuclear fusion just 92,960,000 miles away, but our ability to harvest it is not. Currently the sun provides just 1% of our total energy consumption, and that number is increasing at a snail’s pace. President Obama (that’s nice to type) may indeed see us getting 25% of our energy from renewable sources in 2025 as he hopes, but very little of that is likely to be solar. It is expensive, challenging to integrate and in some places impractical. Also, our demand for energy continues to grow, outpacing new technology as it tries to catch up.

That said, those panels pinned to the roofs of the occasional green building are a beautiful thing. They are a bold move toward making the building a producer of energy rather than a consumer. They represent a potential shift in the way we think about energy delivery. But, they are just a tiny drop in a giant sloshing bucket. Worse, they are often just a drop in the bucket of the building on which they are perched. There are relatively few net-zero buildings out there, far less than the number wearing panels. The energy demand is simply too high. Many people have said it before me, but we need to reduce consumption to make renewable energy effective in the short term. Sure, someday in the future you might be able to leave every light on in your house with the HVAC at full blast and the windows open (so you can hear your music as you lounge in your giant heated pool) and know that all that juice is coming from the sun. But that day is not today.

When people visit our homes they always ask about solar panels (we have solar thermal but not PV). It is an inevitable interview question and an unavoidable conversation. The simple answer is that adding solar PV is simply too expensive. It isn’t in the budget. The longer answer involves a set of priorities which seek to minimize use before investing in production. Even if the money to install solar was available, it might be better spent on improved windows, more insulation and energy saving automation products. Solar PV becomes more feasible as we reduce demand. If the proverbial horse is reduced consumption while solar represents the cart, it seems that many people are still trying to get the horse to push. Horses hate pushing, and we try not to make them do it.

We will have solar PV on future homes (when the state incentives finally come through), and the homes we are building now can easily be retrofitted for solar power. I certainly don’t condemn anyone who makes the investment in solar, and I commend those doing the research to bring us better, more effective options. However, I think adding panels to a building that has not been designed (or retrofitted) to greatly reduce energy consumption is premature. Invest first in the building envelope and systems. Then add solar. It will be much more effective.

What do you think? What kind of potential does solar energy have for buildings? How efficient should a home be before the investment in solar will pay off? How does this extend to society in general? How much of Obama’s 25% will need to come as a result of reduced consumption?

If you have something to say . . . comment.

Problem Statement

The high efficiency Munchkin gas boiler is more expensive to install (>$3,500) than budgeted as both a backup to the Schuco Slimline II-80 solar thermal system spec’ed out for domestic hot water and a sole source of heat to our hydronic radiant heating system (more on these mechanicals here). Installing gas service to the house will also cost an additional $2,000 in permitting fees and additional plumbing costs to run the line inside the house. The high efficiency (97%) of the gas boiler is needed to accomplish a HERS rating of 52 that enables the 100K House to achieve a LEED Platinum rating. Electric alternatives to heating water are not nearly as efficient overall and will dramatically increase our HERS score.

Hypothesis

If we increase our solar thermal system parameters by two more 25 square foot solar panels and an additional 80 gallon storage tank with integrated electric backup heater, we will be able to eliminate the gas boiler while reaching the same efficiency as the gas boiler backup design without increasing overall cost. This design has the potential to be lower in overall cost with the eliminating of any gas service run to the homes at all.

Key Variables

The big hurdle in switching to all electric water heating while still achieving the same HERS rating is the difference in the source to site multiplier between gas and electric. What the heck does this mean? Basically, since the US is so lousy at efficiently generating and transporting electric power to our homes, the HERS rating system multiplies the power used by electric appliances by 3.16 to compensate for the roughly 30% efficiency level we are generating electric at currently. For gas, this multiplier is only 1.02. So, if we are going to replace our gas boiler with an electric backup, we must be three times as efficient in terms of total power used.

We have calculated that we will need to compensate for roughly 67% of our radiant heating demand in the winter with increased capacity in our solar thermal system. This leaves us with just over 2,000 kWh’s of supplementary electric backup heat for the entire year.

Yesterday a three man team from local solar experts, Solaris Energy, sat down with us for a marathon meeting to try and determine if our goals above are possible. We have a proposed design and will be sending it off shortly to the fine engineers at Schuco to see if we are in the ballpark or totally off base. Stay tuned for the update and lots more math.

Just for the heck of it, I had a PV system quoted for the 10K House to see how much it would cost to take care of 100% of the electrical demand with a grid-tied system. The good people at SunPower Builders gave me an estimate today. We would need about a 5KW array to supply all of our electric. The breakdown in cost is as follows:

• 2,800 Watt System – $28K
• 4,000 Watt System – $39.5K
• 6,000 Watt System – $53.9K

To think that just a few months ago, I thought that offering a PV upgrade option to convert an all-electric home to a zero energy home would be feasible.  We are using gas now for both water and space heating and have eliminated A/C and we still can’t come close. We wouldn’t even have enough room on the roof to fit enough solar panels to make it zero energy. This is a bit sobering and a testament to the fact that renewable energy is not the answer.