charging station

Commons’ PV Array Can Support 3 Electric Cars

by Eric Dolven (unit 5)

A couple of years ago, the Clearwater Commons installed a 9.2 kW socharging stationlar PV array on the roof of a shared building.  Since that time, two families have decided to lease Nissan Leaf electric vehicles and use the solar array for charging needs.  Of course the PV system is grid tied, so even if the array did not have the capacity to charge the vehicles, the energy would still be pulled from the grid.  However, I got curious about how many Leaf miles our array could fully support.  So here is the data.

The inverters we installed provide 1 year of on-board data logging, January 1 to Dec 31.  We currently do not download this data.  As a proxy, I simply looked at the inverters and noted that our 9.2 kW array produced about 9000 kWh of electrical energy in 2014.  If we had full, direct sun 24/7, that array would produce 80,592 KWh of electrical energy over the course of one year.  Given roughly half the year is night and half is day, the value corrects to more like 40,300 kWh.  And since solar intensity is roughly sinusoidal, and the average of a sin function over half a period is 2/pi (= 0.64), we could generate a maximum of roughly 25,800 kWh in a year.  So we have about 35% efficiency based on the 9.2kW specification.  This reduction is primarily a function of the cloudy weather in the winter months.  Functionally, the array is a 3.2kW system.

IMG_1162So back to the question of how many Leaf-miles the array can support.  To answer this, I have started monitoring the energy efficiency of our Leaf.  On average, the on-board computer reports our personal driving habits yield about 4 mi/kWh.  Based on this, the 9000 kWh annual budget provided by our PV system would allow us to drive 36,000 miles per year.  With a 12,000 mile limit stipulated in our lease agreement, this would allow three Leafs to be charged, fully supplied by our PV array.

Of course, there is a hitch.  The efficiency value I used is based on the car’s output; into how many miles does the energy stored in the batteries get converted.  Behind this is the issue of filling those batteries.  Charging is not a 100% efficient process.  If we charge the car on the 110V charger that comes with the car, we actually get 2.7 to 3.0 mi/kWh.  Using these numbers, the PV array can only provide 24,300 to 27,000 miles.  Closer to two Leafs.  The balance gets lost in the imperfect battery charging.  But the story isn’t over.  Charging with a 240V charger is much more efficient than with 110.  But right now, I don’t have a good way to measure the charging of the 240V charger.  So the true answer is that we could support more than two, but no more than three Leafs on our solar PV system.

An interesting side note is that if we use the solar p20150203_115526ower to fully charge those three hypothetical Leafs, it would save us 1200 gallons of gasoline each year (assuming cars that get 30 MPG).  That converts to roughly 13 tons of CO2 gas that is not being released into the atmosphere.

Green Home Tour & Free Workshops

This Saturday – April 26, 11am-5pm – Clearwater Commons is a featured as a site on the NW Green Home Tour. Come by to tour our homes, shop, gardens and creekside acreage. While you’re here, join our free workshops, scheduled throughout the day.

Free Workshops:

Adding the Solar Asset: Powering an Electric Car with a Solar Arraycharging station
11:30pm at the shop

This workshop presents the basics of setting up a photovoltaic solar array on your home to power an electric vehicle (or anything else). Using the Commons’ set up as a model, you’ll everything from getting State approval to prepping the site to maximizing rebates and tax breaks. Charging station available!




The Pin Foundation Advantage
2:30pm at unit 8pin piles 5

Most units at Clearwater Commons are built on pin foundations: a solid pin pile foundation that reaches deep into the ground without digging holes or pouring concrete. Simple to install, these foundations avoid excavation, thus reducing concrete use, saving fuel and precious topsoil, while preserving natural drainage.


Reclaimed Wood Finishes in Unit 5
3:30am at unit 5

Eric woodwork

Lower your consumer footprint and save money by using reclaimed wood throughout your house. Unit 5 spun stories into their finishes with antique Douglas Fir from a 1894 Poulsbo house, Madrona from a conservation easement on Vashon Island and a variety of species from an “urban sawyer” in Tacoma (to name a few). Come see the result while getting tips, advice and sources of wood.


What’s Up at the Commons

The warming temperatures, rain and turn of the season has things popping UP all over the place at the Commons. Frogs music’s turned up loud through both day and night.


peas creeping up toward the mini-B deck near the herb garden

native plantings along the W fenceline

native plants staked up along W fenceline, replacing blackberry & barbed wire


carrot canoe filled up with fresh soil, ready for worm castings then seeds


North Creek up almost as high as fall 2012 when the carrot canoe washed downstream to our shores

trellis soon to go up in the orchard

trellis soon to go up in the orchard, where there are several new trees, shrubs & berries


double rainbow up over (future) units 9-12; imagine living somewhere under a rainbow (or two)







Energy Cost of Unit #5

by Eric Dolven

We’ve been living at the Commons for almost a year and I’ve been curious how energy efficient our house really is.  We spent extra money for a ductless mini-split heat pump, double paned Anderson-100 windows, a heat recovery ventilator, (all pictured here) blown in fiberglass insulation, energy star lighting and appliances, and I’m getting curious how much our energy bills are reduced by these measures.  Of course I can’t answer that question because this is a new house, but I can compare how much we are paying now versus how much we were paying at the same time last year in our old, leaky, drafty Seattle house. IMG_7865

Since we don’t have a gas line anymore, all of our energy comes in as electricity.  Heat, hot water, cooking, lights.  So it’s hard to single out heating costs.  But assuming the largest utility cost comes from heat and that we are lighting and using hot water in the same way, it’s probably fairly accurate to compare total energy cost of the old house with total energy cost of the new house.  So what


I’ve done is gone back and compared our utility bills from roughly June 1, 2012 (when we moved in) to the present, with the equivalent bills from the same time the previous year.

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Yellow Brain Fungus, Water Ouzel & Snowberries

by Shawna Lee

After many hours of rain, North Creek was overflowing its banks again, although it was not as high as it was a few weeks ago. Bob and I walked down to the creek edge this morning to see it. The power of that much water always feels exciting, and it’s fun to see how the bigger volume of flowing water has changed and shifted the contours of the banks and stream bed, not to mention loose objects beside the creek like the logs of the fire pit.

Looking upstream


Cinclus mexicanus

A cute little American Dipper was bobbing up and down at the flooded edge of the creek. It is such a soft gray and blends so well into the background of gray water that I didn’t see it until I had gotten fairly close to it. I stayed still and with no alarm, it continued to bob and poke into the shallow water for aquatic insects, their larvae, and maybe even tiny fish.

The Salmon Return

by Bob Freeman

We recently heard that salmon were spotted in North Creek downstream from the Commons in Bothell. The water levels were a bit low and we were concerned that the fish would have a hard time swimming up to our neck of the woods. This last week, we finally saw some good rain and the stream levels rose.

Early in the week, Eric sent out word that he spotted one on the property. The next day, Tom reported seeing five in the quieter part of the stream on the west end of our part. Saturday, Shawna took me down during her regular Salmon watching time. (She is a volunteer “Salmon Watcher” for a multi-juristictional partnership of local cities and King County). Armed with a camera and some very silly cardboard salmon watching glasses — they are polarized and actually help cut glare on the water — we went down to the west end of the stream.

It was not long at all and we were rewarded by spotting 3 Coho salmon. I turned on the camera and even put one of the polarizing lens from my glasses in front of the camera lens. Take a look at the video below:

It is exciting to see them after all the restoration work that was done last year. The creek is now well suited for Salmon spawning. It is hopeful to see so many this year.
– Bob

The Clearwater Commons Story: Turning Low Impact Development into Positive Impact Development

By: Tom Campbell
October 2011

The author was one of the principal architects of the Growth Management Act (GMA) in 1990 and a member of the Governor’s Land Use Study Commission. He is a consultant on public engagement strategies, a judge for the Governor’s Smart Communities awards, the chair of the Charlotte Martin Foundation, and a member of Clearwater Commons.

This is the story of a growth management policy wonk turned developer. It is a high anxiety story of a successful effort to build one of the most comprehensive green low impact developments (LID) in the Puget Sound area – through some of the laws I helped to create. This arduous five year journey was made even more difficult by a housing recession; a complex web of new and complicated regulations; and, a reeling banking industry.

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