Could Earthaven Ecovillage, in the Southern Appalachian mountains in the US, become, as GEN advocates, “Fossil-Free by 2020”? With its new “off-grid Microgrid” system, one of Earthaven’s 13 neighborhoods, the Hut Hamlet, is well on its way. Diana Leafe Christian reports. (A shorter version of this article first appeared in the Winter 2015 issue of Permaculture Magazine.)
A “microgrid” is a small localized grouping of electricity sources and loads which can function autonomously without the regional power company. Its electricity is compatible with the local grid and is usually connected to it. But the Hut Hamlet’s Microgrid uses off-grid photovoltaic (PV) power for electricity (and sometimes for hot-water heating), and stands alone as its own small power company inside an ecovillage.
The only fossil fuel the Hut Hamlet now uses is propane for the neighborhood kitchen’s cookstove, and as a back-up to heat water for the neighborhood bathhouse.
Earthaven is an off-grid ecovillage already, with individual residences, multi-household dwellings, and it’s shared community building off the grid now, deriving electric power from PV arrays and a central micro-hydro system. But the Hut Hamlet’s new Microgrid now provides more power for more functions for its 11 households more reliably than ever before.
The Microgrid’s Four Functions
(1) More Electric power. The Microgrid provides each residence and their shared kitchen/bathhouse with more kilowatt hours of electricity than when each building was powered by its own individual PV system.
* 8.16 kW: Photovoltaic systems are described by how many kilowatts (kW) they generate at any one moment with full sun on the solar panels. The Hamlet’s new Microgrid is an 8.16-kilowatt system.
* 31.5 kWh: A “kilowatt hour” (kWh) is a measurement of energy, or power over time, and is used to measure how many kilowatts are required to run a household or other building. The Microgrid’s array of solar panels, located in this specific location, according to the “PV Watts Online Calculator,” will produce 31.5 kilowatt hours on an average day1.
* 11 times fewer kilowatt hours than the average American home: The ecovillagers at Earthaven are so resource-conserving that all 11 households combined use no more kilowatt hours than one average home in the US — about 29.9 kWh a day2.
With the new Microgrid Hamlet residents usually have more than enough power for their needs. “Now on sunny days I can iron my clothes,” says Suchi, “and use a decent vacuum cleaner that won’t blow the system.”
(2) Saving propane — hot water. Designing a correctly sized battery3 can be challenging. If the battery is too small for the number of solar panels and thus the amount of power generated, it’s nearly useless. But if too big for the number of panels, the battery won’t adequately recharge after a series of cloudy days, which reduces battery life, and batteries are expensive to replace. On the other hand, if the system has enough panels to recharge the battery quickly after cloudy days and to keep it well-charged, during a series of sunny days much of the electricity will go to waste. And to protect the battery from damage by being overcharged, the system literally disconnects the battery from the panels.
The Microgrid resolves this dilemma with an “overly sized” array of solar panels. All extra electricity generated after a series of several sunny days is diverted to heat water in a well-insulated electric hot water heater in the kitchen/bathhouse. Hamlet residents need only read the tank’s dual read-out thermometer at both the top and bottom of the tank to know when there’s plenty of hot water for a shower.
(3) Saving propane – cooking. Every kitchen in the Hut Hamlet has a propane kitchen stove. But with the Microgrid, after a series of sunny days gives the battery a high state of charge — which anyone can check on the digital battery meter — so there’s actually enough extra electricity to save propane by cooking with electric appliances like crock pots, rice cookers, waffle irons, bread ovens, toaster ovens, and so on.
(4) Better Internet Access. Currently the 22 Hut Hamlet residents make do with five slow Internet connections and the local telephone company won’t add any more. The neighborhood also added new phone lines to each hut in the same trenches as the new electrical lines, so all of the new phone lines meet at the same hub from which their electricity is distributed. With the Microgrid’s electrical lines spread throughout the neighborhood, the residents will be able to combine all Internet connections through a load-balancing router, and send Internet signals to all residents through “Ethernet-over-powerline” technology. Every residence will have access to high-speed Internet without paying extra on their phone bills.
Starting the Microgrid
After repairing photovoltaic systems for the Hamlet’s 11 households for more than a decade, in early 2014 two solar electricians, Chris Farmer and Brandon Greenstein, had received far too many emergency calls from too many Hut Hamlet residents begging them to troubleshoot, repair, upgrade, or otherwise cobble together a temporary low-cost fix for their many small, inadequate, non-code, often malfunctioning, owner-installed systems.
Farmer (called “Farmer”), a longtime Earthaven member, and Brandon, a former ecovillage member and neighbor, knew the Hamlet’s off-grid systems very well, and also knew the owners’ financial challenges.
“It would make a lot more sense and be cheaper in the long run,” Farmer recalls, “to start fresh with a new, state-of-the-art off-grid system wired to electrical code standards that would provide more than enough power for the entire neighborhood.”
So he designed an integrated, expandable system for the Hamlet with 32 photovoltaic (PV) solar panels, a large battery, two charge controllers, two inverters, and a backup generator. Every household would be individually metered. One inverter would be “asleep” 90 percent of time, activating only when the main inverter needed greater capacity. A back-up gasoline generator would provide power whenever the percentage of battery charge dropped too low. The new system would cost approximately $52,000 for equipment and labor, with additional costs for trenching and legal fees.
“It took a while for the social and economic implications of the idea to sink in,” recalls Hut Hamlet resident Kim “Kimchi” Rylander. It would require us to cooperate and coordinate our efforts to a greater degree than we had before, and many were intimidated by the cost.
Kimchi contacted the Appalachian Institute for Renewable Energy (AIRE), a local nonprofit which helps churches, local governments, and other community groups develop and fund affordable renewable energy systems. At first it looked hopeful, but ultimately the Hut Hamlet didn’t qualify for AIRE’s financial help. For awhile Hamlet residents were discouraged and let the idea drop, but then Farmer suggested they could simply raise the money themselves, which they did, with most residents securing loans from family and friends, including from other Earthaven members.
The Microgrid equipment would be owned by a co-op. Hut Hamlet residents Suchi Lathrop, Zev Friedman, and Gabriel Vierra, drafted its ByLaws. To ensure the co-op’s continued existence over time, they attached co-op membership to each specific residence rather than to any individual or household.
Hamlet residents wouldn’t contribute equally to the $52,000 cost. Rather, each would contribute a differing amount, ranging from about $2,000 to about $6,000, representing that household’s percentage of estimated electrical usage relative to the other users. To determine this, each household estimated the likely amount of electricity they would use each month, based on the kWh of their current and estimated future electric loads. Those with fewer high-load appliances would pay less, and those using refrigerators, freezers, and vacuum cleaners would pay more.
Different households use different amounts of electric power each month. And in an off-grid system, people have varying levels of awareness about how much electricity they’re using at any given time relative to how much power is left in the battery (its “state of charge”) and relative to electricity-generating capacity: sunny day or nighttime, a recent string of sunny days or of cloudy days.
To address this dilemma Farmer designed a weighted system of measurement, so the amount each household would pay monthly would depend on the amount of their electrical use relative to the battery’s state of battery in real time. Initial capital contributions as well as ongoing operating expenses would be determined by this method, so that those who are less conscious about their energy use would pay more overall for the system’s cost.
A specialized software system that coordinated several interacting components for the weighted system was developed by Earthaven resident and computer programmer Jake Ferina. It took, Jake said, “2000 lines of code, 7 months of my life, and over 400 hours of work.” Famer considers his automatic generator-start program for back-up power better than any similar commercial program currently available.
All this took about a year. In May, 2015, Brandon and Farmer, with labor help from various Hamlet residents, mounted the solar panels in a small field above the neighborhood’s graywater ponds and installed the large battery, inverters, and other solar electric equipment in a small room behind the kitchen. Hamlet neighbors saved money by digging trenches for electrical lines through their gravel roads themselves with a rented trencher. They threw the switch in early June, 2015. The Microgrid was on!
Kimchi serves as bookkeeper, taking meter readings and charging each household their percentage of a monthly fee for a fund to maintain and repair the system, and to replace its equipment in an estimated 20 years. Farmer provides minimal monthly maintenance, though he will soon train a Hamlet resident to replace him in this task.
Future plans include adding a load-sharing router for better Internet access; being able to read online the percentage of battery charge, temperature in the water heater, and meter readings for individual households; and potentially adding a micro-hydro turbine in a nearby stream to increase electrical capacity as new residents join the Hut Hamlet.
Fossil-Free by 2020?
“I see the Microgrid as an art project,” says Farmer. “It draws from a palette of all these various technological and engineering concepts and practices. The point is to show people how much they’re using the sun’s energy and impacting the battery, instead of what solar technology usually does, which is to blind us to our impact on nature in our use of electric power. So the Microgrid has the kind of technology that makes us conscious of our connection to nature.”
Ideally, each of Earthaven’s neighborhoods will develop their own Microgrid systems, inspired by these pioneering efforts. And, while not entirely free of propane yet, ideally someday the Hut Hamlet and every other Earthaven neighborhood will replace propane with effective sun-based technologies for cooking and water-heating (perhaps inspired by those at Tamera’s Solar Testfield in Portugal). And . . . perhaps everyone at Earthaven, not just a few, will use car-sharing co-ops and biofuels to drive to town.
And if these ideal scenarios come to pass — perhaps by 2020 — this ecovillage will truly be fossil-free.
1 According to “PV Watts Online Calendar.”
2 In 2013.
3 Whether one large battery or a number of smaller batteries wired together, the term is “battery,” singular.
Sidebar 1: “Weighted” Payments
Here’s how this works. After every 1.25 watt hours of electricity a household uses, its meter sends a pulse to a central microcontroller. The microcontroller multiples the 1.25 watt hours by a factor of between 1 and 11, depending on the battery’s state of charge at that moment. When the battery is at its highest state of charge, such as after many sunny days, the 1.25 watt hours of electrical use is multiplied by 1. And when it’s at its lowest acceptable charge, such as after a series of cloudy days, the 1.25 watt hours of electrical use is multiplied by 11. The 11 gradations of this multiplying factor depend on the battery’s state of charge at any given moment. So the electrical use of each household is repeatedly monitored as to how much power the household is using relative to the current state of battery charge. This multiple of 1.25 watt hours is what the household pays as their watt hour usage for the month. Thus people who use the toaster and vacuum at midnight pay considerably more than those who perform these tasks only on sunny days.
Sidebar 2: Microgrid Specifications
* 8.16 kW solar photovoltaic array – 32 individual 255 watt Kyocera panels.
* 48 volt 950 Amp Hour HUP Solar One brand flooded lead-acid battery
* Two MidNite Solar 200 charge controllers
* Two Schneider Electric XW6848 inverters, each capable off-grid, or grid-tie-in with battery back up, and each capable of 6.8kW of continual power output of conventional US 120/240 volt AC power.
* 105-gallon, 240 volt AC electric hot water heater
* Super-quiet gasoline-powered Honda EU7000is generator
Diana Leafe Christian, a GEN-US ambassador for the Eastern US, is author of “Creating a Life Together: Practical Tools to Grow Ecovillages and Intentional Communities and Finding Community”. Diana speaks at conferences, offers consultations, and leads workshops internationally on creating successful new ecovillages, how existing ecovillages succeed and thrive, and governance and decision-making in community. She lives at Earthaven Ecovillage in North Carolina. http://www.DianaLeafeChristian.org