Energy infrastructure and conservation methods are foundational to the creation of self-sufficient and self-propagating teacher/demonstration communities, villages, and cities to be built around the world. This page is an open source and free-shared guide to the setup and expansion of off-grid energy infrastructure during the construction of teacher/demonstration hub food infrastructure, village models, the Duplicable City Center, and beyond. Once on the property, we will further evolve the Highest Good energy® foundations and open source resources with additional implementation and research results of an even broader diversity of energy saving strategies and alternative energy infrastructure methodologies.
This page contains the following sections related to Highest Good Energy:
One Community defines Highest Good energy as renewable and conscientious of the air, water, and land that we all share. It is also an active approach to energy saving strategies that we are implementing including semi-subterranean building, shared social spaces, passive heating, cooling, and lighting, maximally efficient hot water heating, water saving shower heads, energy saving lighting plans, and more. One Community’s Highest Good energy rollout is detailed below assuming zero initial energy infrastructure and starting with traditional generators, then building a comprehensive solar array, and expanding with the exploration and implementation of wind and newer technologies as they become available and can be determined to be superior to other alternatives.
The current global approach to energy is not sustainable. One Community sees open source sharing the complete off-grid setup and expansion of energy infrastructure for beginning teacher/demonstration hubs through well-established hubs of 400+ people as a needed and desired stepping stone to global energy sustainability. Our goal is to promote conservation, all sustainable energy providers and technologies, and the viability of complete energy sustainability. We see making small-to-large group energy self-sufficiency easier, more affordable, and more attractive as part of our comprehensive approach to evolving sustainability that will positively and permanently transform the world for everyone.
Doug Pratt: Solar Systems Design Engineer
Lorenzo Zjalarre: Physicist and Energy Efficiency Expert
Ramya Vudi: Electrical Engineer
Robert Seton: Solar Design Engineer and Owner of Solar Hybrid Design
Ron Payne: HVAC/Thermal Designer and Mechanical Engineer
Shubham Agrawal: Electrical Engineer
We are beginning with open source and free-sharing comprehensive strategies for energy setup and conservation through semi-subterranean building, shared social spaces, passive heating, cooling, and lighting, maximally efficient hot water heating, water saving shower heads, energy saving lighting plans, and the detailed energy infrastructure rollout and establishment plan outlined on this page. As we complete them, the open source resources list below will continue to expand with tools, tutorials, and DIY resources for duplication of all aspects of One Community’s energy infrastructure:
|What we’re working on now|
|Energy self-sufficiency phase-in for 20-400+ people|
|Solar array cost analysis and implementation details|
|Resource saving and efficient Duplicable City Center|
|Hydronic systems setup and development for 20-100+ people|
|Dome-home heating and cooling research, plans, and adaptations|
|Shower dome and toilet dome energy efficient water heating specifics|
|Highest Good lifestyle considerations and conservation strategies|
|Water-saving shower head research and comparison strategy|
|How to make your build easier than ours and how to solve any problems we encountered in our build|
|Complete and on-going maintenance and upkeep details per our experience with all energy infrastructure components|
|Archive and database of others building similar structures including their experiences, adaptations, etc.|
Before One Community (or any off-grid teacher/demonstration community, village, or city) can begin being constructed in earnest, an initial team will need to move to the property to survey the land and begin food infrastructure preparation, finalize development plans, and create the “pre-infrastructure” that needs to exist to support the construction of the official One Community infrastructure. This group will need access to electrical power before much else can be done. From that point forward, more extensive and permanent infrastructure will be built.
What follows is the specific plan for this energy rollout starting with the initial survey team of 0-20 people through our first 400. As part of our open source goals, this rollout is designed and described in detail to help those interested in duplication. Additional details will be added as we
Note: We are seeking further professional input to double check our work on sections in blue – join our team if you’d like to help. Prices are accurate as of 9/2014.
The primary focus of the solution for the initial people to move onto the property must be providing electricity as quickly as possible. There is also a need for flexibility of the generated power in order to provide the group with access wherever we need it. This will be accomplished initially by diesel generators with a plan to purchase our battery banks and begin construction of the solar array the second month.
|Equipment Needed for this Phase||Cost||Details|
|100 kW generator + add-on options||$22,124||100 kW generator (2400 kWh/day possible) – see efficiencies chart below|
|Towable Fuel Tank||$12,900||990 gallon towable fuel tank|
|Fuel cost for 1 month||$2,480||Running at 16.8% for 5 hours/day (see below for details and efficiency graph)|
Note: Eventually the generators will be mounted permanently on slabs. Ideally we will also be able to phase them out completely at some point. This, however, will be the focus of future engineering endeavors and is therefore not discussed at this time.
In the beginning, the power needs will vary too much from day to day to start building longterm energy infrastructure. However, since the generators will be on trailers, we will be sure to have access to the required electricity when and where it is needed:
Select # of gen-sets and their capacity: Current estimate of total capacity needed to cover the instantaneous power draw for the Earthbag Village and Duplicable City Center is ≈400 kW. To provide the flexibility to supply power where it is needed, the total capacity can be provided by multiple units (one 100 kW generator + two 175 kW generators = 450 kW total). At about a ton each, these would probably be best used on trailers for mobility. Later installations of generators would be permanently mounted on slabs.
The reasoning behind having a 100 kW gen-set first is that it will provide intermittent and mobile power for use on miscellaneous work sites throughout the property. The two 175 kW units would then be slab-mounted near the Duplicable City Center and the Earthbag Village (Pod 1), mostly to provide backup power for the Duplicable City Center which will service the most people and consume the majority of the power we generate.
For easy fuel storage, a trailer would provide mobility for frequent refueling at a biodiesel fueling station or delivery service. For more permanent storage a bladder might be the best and most low-cost solution.
Note: Fuel consumption per generated kW varies with electrical load when using a generator. The chart above shows average fuel consumption in relation to % output (load). Since this chart is for a 100 kW unit, the % load is equal to the kilowatt output (50% = 50 kW). We will be able to use this data as a guide to size the fuel source.
After the “landing party” has completed their site survey, identified the locations of all planned construction (specific for buildings to be built in first 5 years, plus long-term general plan), begun working on the infrastructure, and completed and gained approval for all the initial building plans, the rest of the Pioneer Team will move onto the property. At this point, enough planning will have been done to begin working on the long-term energy infrastructure while still allowing for flexible power generation for construction needs. This means beginning to build the entire solar array to eventually service the Duplicable City Center and Earthbag Village (Pod 1).
|Equipment Needed for this Phase||Cost||Details|
|175 kW generator + add-on options||$24,949||175 – 275 kW (4200 – 6600 kWh/day possible with one 100 kW generator and one 175 kW generator)|
|1000 gallon Fuel Bladder||$2,406.69||1000 gallon fuel bladder|
|Fuel for 6 months 175 kW Gen or (100 kW generator)||$20,248.70 ($14,624.06*)||@28.6% for 4.2 hours per day (@50% for 4.2 hours / day*)|
|Energy Manager||$14,294.00||SMA, Multicluster Box, 3-Ph for 12 x 120V, 60 Hz,
SI5048U, add MC-PB, UL listed off-grid only, MCB-12U
|Solar Array X3 (with batteries)||$1,419,926.88||283 kWh (849 kWh/December day)|
* This is smaller for the same amount of energy production due to the increased efficiency of these generators when running at a higher percentage of its maximum.
Power production at this phase of construction will include implementation of the complete energy infrastructure needed for powering the Duplicable City Center and Earthbag Village (Pod 1). The portable generator will be used for tool and other remote power needs, and main-site needs, until solar is installed and operating as the primary power supply for the Duplicable City Center and Earthbag Village (Pod 1) sites:
First we will install the batter bank and power management systems so it can be charged using the generators. We will then begin our transition to solar power by connecting the solar array to the system as quickly as possible to decrease use of the generators.
Note: The battery bank does not need to be full size yet, but must have the capability of increasing to that size in the future.
Based on our energy needs we will also:
Here are the 175 kW generator power efficiency and production projections for comparison with the chart above. Comparing these projections will help us maximize efficiency and minimize fuel use for our generators.
By now, construction of the initial components of One Community are in full swing and we’re ready to bring on additional team members to accelerate the pace of progress. Along with population increases we will see the demand for electrical power and hot water increase. For instance, the Duplicable City Center kitchen and large-scale laundry facility will both be fully operational during this time and draw considerable electric power. As the demand grows, we will increase taking advantage of the energy efficiencies that are associated with larger systems like these and implement additional energy reduction and conservation measures too.
|Equipment Needed for this Phase||Cost||Details|
|175 kW generator + add-on options||$24,949||175 – 350 kW (4200 – 8400 kWh/day possible with both 175 kW generators now up and running and the 100 kW generator as a more mobile backup)|
|1000 gallon Fuel Bladder||$2,406.69||1000 gallon fuel bladder|
|Fuel for 6 months 175 kW Gen or (100 kW generator)||$25,284.10*($29,248.13)||@50% for 4.8 hours per day* (@50% for 8.4 hours / day)|
|Wind Turbine(s)?||??||We will have the necessary experience with our location to effectively evaluate this option by this point|
|Flow Battery | Forbes Article About This||??||This technology (or other large-scale options) should be ready for market by this time|
|Total||52,639.79||This number will meet our needs and the addition of wind turbines, flow batteries, or other options will only be considered if proven financially and sustainably superior to other options|
* This is smaller for the same amount of energy production due to the increased efficiency of these generators when running at a higher percentage of its maximum.
As development continues, the hydronic systems become operational and the total load on the Energy Manager will increase. As energy saving measures are added, the load will decrease. Overall, our total demand for power, both hydronic and electrical, will increase. This construction period will be very energy-intensive and will require large amounts of fuel. The Duplicable City Center radiant heating will be the largest consumer of power (both hydronic and electric). Therefore, it will be beneficial to have the core energy system (all solar arrays) and some of the energy-reducing measures in place before the hydronic system is enabled. Further evaluation on the property will dictate whether wind power solutions are viable.
The following are the action steps for this phase of energy infrastructure development:
Related to the last bullet-point above, here are the viability projections for energy storage starting with small amounts of energy being stored for less than a day and progressing to megawatts being stored for a year or more. The red line is our power demand and what you see is that with storage capacity there is an amount of stored energy that can offset cost in the different mediums: batteries, compressed storage, etc. If we need to store power for 1 month, batteries are not a viable solution, but hydrogen storage would be once energy storage needs are sufficient to warrant the added expense of creating infrastructure like this.
Throughout the first five years on the property, One Community will construct several key structures. These will include the Duplicable City Center, the Earthbag Village (Pod 1), Straw Bale Village (Pod 2), food greenhouses, and additional village models if possible. The expectation from residents working in these areas and visitors touring our community will be that the solutions we are testing and displaying are genuine and practical solutions. During this time the Phase I energy system (described above) will be completely developed and the new focus will be testing and monitoring this system, fine tuning and conservation strategies, and planning and implementation of next steps.
|Equipment Needed for this Phase||Cost||Details|
|To be determined||TBD||We will choose this development phase of energy infrastructure based our open source duplicability goals and global transformation values and strategy. It will be paid for by our revenue streams.|
This phase of development will be about monitoring all electrical energy being consumed and making expansion decisions based on needs and what we learn. The monitoring will be accomplished through meters for all individual living spaces and ammeters on any main power lines that would output the amps being used at that instant. Since the voltage will be known, the power will then be a simple calculation done by either a designed system or one bought off the shelf. That power (in Watts or kW) will then be logged over time to get the amount of energy in kWh used during the course of the day.
The following picture illustrates this with each “A” representing a monitoring point that communicates with a power display feeding data to central data analysis point:
Electrical Power Monitoring will have displays at the source and connections to a Main Power Display that will monitor and control electrical energy management sub-system.
Similarly, hot water used in showers, domestic use, and hydronic systems can be monitored by knowing the flow rate, temperature, and amount of time used. With instantaneous water heaters at points of service, the electrical energy draw from those units could also be used with the addition of the known hot-tank water temp and the flow rate of the use.
In short, hot water monitoring needs two pieces of data for each point: temperature and flow. For showers and the boiler, temperature can be replaced by an electrical power reading which will already be monitored by the electrical energy monitoring software and relayed to the Main Power Display. For everything else, temperature and flow monitors will do the job.
Specifically monitoring all of these things will allow us to fine tune our consumption patterns and open source share our results. Tracking these metrics for guests will also be a major benefit to the mission of One Community by showing the constant flow of temporary residents/visitors an accurate report of their energy usage while staying. In so doing, we help to educate people and give them the opportunity to become more conscientious about their use.
This will also create ultra-accurate energy needs assessments to help us with our planning and construction of each additional open source village needed for expansion to host people beyond the initial 400.
Sustainable energy, and renewable energy abundance, is all about careful planning and system redundancy. We won’t be able to effectively plan our power needs beyond the Earthbag Village (Pod 1) and Duplicable City Center until both of these components of our infrastructure are complete and we’ve gained the experience of using the systems designed above. While it is predictable that we will actually increase our energy efficiency over time due to increased conservation methods and “fine tuning” of our usage patterns, it is also predictable that we will have energy needs we haven’t accounted for.
Learning from experience, learning more about our specific property and how effective options like wind power may be, possible implementation of new energy technologies, and a better understanding of our specific needs will all be crucial to planning our power infrastructure for the Straw Bale Village (Pod 2) and beyond. Here are a few options we’ve explored to demonstrate cost differences and energy production potential.
Wind power is provided by turbines, which convert mechanical energy into electrical energy. Depending on how windy a property is, wind power can be a good complement to solar because it can provide energy 24 hours a day. Typically on an off-grid system wind power is used to charge the battery bank of the solar system at night. Below is a table listing some typical wind turbine capacities and costs:
Another lesser-known solar technology is the solar salt pond. The solar salt pond uses a salinity gradient to trap solar radiation in a large pond. The water heats up to 200 degrees Fahrenheit (93 degrees Celsius) and remains on the bottom of the pond due to the salinity of the water. This hot water can be used to heat liquids through a series of pipes on the bottom of the pond. The liquid in the pipes can in turn heat directly or produce electricity through an Organic Rankine Cycle Engine.
Several solar salt ponds have been demonstrated in Israel, Texas, and Australia. A half-acre solar salt pond with a depth of eight feet (2.4m) could provide 20 kWh of electricity day, night, summer, and winter.
The costs in constructing such a solar salt pond are listed below.
The advantages of using a solar salt pond for generating electricity include: no fuel costs, low maintenance, and 365 day/24-hour power generation. Disadvantages include: danger of spillage of saline water to environment, high initial investment, and large land usage.
We’ve already designed an extensive hydronic system that includes solar hot water. Expanding this system in the most intelligent manner possible will be based on our experience with the first system, technology advances, and clarification of expansion needs. As with solar PV systems, solar hot water systems are modular and this will provide us increased opportunities for expansion as our requirements and initial hydronic systems function and effectiveness becomes clear. For comparison, here are a couple typical solar hot water systems and their capacities.
We are contacted almost monthly with a new energy option. Once we are on the property we will have all our team in place and people can bring these ideas to demonstrate them. If we can verify a working model from someone willing to open source and free-share it with the world, we see no place better than an organization like ours to do so. We’ll also be able to consider funding addition research of such systems at that time.
One Community’s off-grid energy infrastructure to supply the Duplicable City Center, the earthbag village (Pod 1), and aquaponics sustainable food infrastructure was initially assessed to require 283 kWh of power and we sized our photovoltaic solar power system to meet these needs. As per the energy self-sufficiency phase-in for 20-400+ people section above, these original assessments have proven far insufficient for our needs. Until we have completed our new needs analysis, we include here the details for the original system purposed to produce 283 kWh/day under average December sun conditions at the One Community property.
We have chosen a photovoltaic system as our initial energy infrastructure because these systems are dependable and capable of being shipped and duplicated anywhere in the world. We will use generators (as described above) as back-ups to this PV system and intend to explore, demonstrate, and open source share whenever possible a diversity of additional energy options (see below) for expansion of our energy infrastructure for the straw bale village (Pod 2) and beyond.
NOTE: THIS PAGE IS NOT CONSIDERED BY US TO BE A COMPLETE AND USABLE TUTORIAL UNTIL
WE FINISH THE COMPLETE DUPLICABLE CITY CENTER AND EARTHBAG VILLAGE (POD 1)
BUILD AND ADD ALL THE VIDEOS AND EXPERIENCE FROM AN ON-SITE ELECTRICIAN
AND THE ENTIRE BUILD TO THIS PAGE. IN THE MEANTIME,
WE WELCOME YOUR INPUT AND FEEDBACK
The following price quote is current as of January 2013.
|Item||Description||Qty.||Unit Price||Ext. Amount|
|PV-based power system designed to deliver approximately 283 kWh/day under average December sun conditions at the One Community property|
|110-0053||Suniva, 250W PV Module, TE F-M0 PV Wire, 46mm Clear
Frame, 60 Cell Mono, 15A Fuse, 223.2W PTC,
*** Wire PV array as 32 series strings of 12 modules each.
2 strings per SB6000US inverter.
*** ProSolar ground racking for 96 columns of 4 modules each
detailed below. 1.5” steel pipe to be supplied locally.
|210-0600||ProSolar, Support Rail, 3”
Extra Deep support rail, 164”, Qty. 1, R-164XD
|240-0178||ProSolar, U-Bolt Assembly,
Clear, Qty. 1, A-UAS-1S
|211-0200||ProSolar, End Cap, 3”,
Clear Anodized, XDeep Channel, Qty. 1, A-EZECAPXD-1
|260-0029||ProSolar, End Clamp 1.810”
(45.9mm-46.4mm), Clear, Qty. 1, C1810EC-1
|260-0046||ProSolar, Mid Clamp 2.50”
(42mm-48mm), Clear, Qty. 1, C250IMC-1
|590-0011||Wiley Electronics, WEEB Grounding Lug
with 1/4” mounting hardware, WEEB-LUG-6.7
|590-0012||Wiley Electronics, WEEB Grounding clip
for ProSolar, WEEB-PMC
|550-0009||Die Co, Cable Clips, Galvanized, Qty. 100, DCS-897-M565 Clip||12||26.07||312.84|
|550-0036||USE-2 Cable, 10AWG,
7-strand 600VDC, black, 3000’ spool, 10-7-3000-sgl
|550-0126||TE Connectivity, SolarLok Plug with Machined Pin, 4.5-6mm
OD,10AWG, USE-2, Female Negative (Blue), 6-1394462-4
|550-0127||TE Connectivity, SolarLok Plug with Machined Pin, 4.5-6mm
OD,10AWG, USE-2, Male Neutral, 7-1394461-5
|550-0363||Rennsteig, Crimping Pliers, TE (TE Solarlok),
with Dies & Locator, Solar AWG 14/12/10, R624 817 3 1
|310-0393||SMA, Sunny Boy 6000TLUS 1-Ph Grid Tied Inverter, 6000W,
208/240VAC, 60Hz, DC Discon, 6 Dual Fused Input Combiner,
1 MPPT, 10 Yr Warr, Ungrounded, Arc-Fault Protection,
|570-0028||SMA, Communication Card, RS-485 Module, SB RS 485-N||16||104.50||1,672.00|
|500-0114||SMA, Multicluster Box, 3-Ph for 12 x 120V, 60 Hz,
SI5048U, add MC-PB, UL listed off-grid only, MCB-12U
|500-0116||SMA, Multicluster Communications (Piggy-Back) Card,
One for each SI Cluster Master, MC-PB
|311-0040||SMA, Sunny Island 6048 battery inverter, 5750W, 120VAC,
60Hz, 56A Transfer, 48VDC, Sinewave, 100A Charger,
5 Yr Warranty, with BTS, SI6048-US-10
|500-0020||Outback, FlexWare 500 DC Enclosure with Ground & Pos Bus,
500A DC Shunt, FW-BBUS, for 1 to 2 Inverters, FW500-DC
|530-0026||Midnite Solar, Circuit Breaker, Panel Mount,
175A, 125VDC, 1-Pole, 1.5” Wide, 3/8” Studs, MNEDC175
|430-0023||Cobra, Battery Cable, 2/0 AWG, Black, 600V,
THW, by the foot, Code Approved, 2/0-X-FLEX-B
|440-0025||Quick Cable, Magna Lug,
2/0 Straight Lug, 3/8”, Qty. 1, 6420-F
|440-0066||Power Panel Component, Quick Cable Heat Shrink,
4-2/0AWG, Red, Qty. 1, UL Listed, 5614-001R
|440-0067||Power Panel Component, Quick Cable Heat Shrink,
4-2/0AWG, Black, Qty. 1, UL Listed, 5613-051B
|430-0025||Cobra, Battery Cable, 4/0 AWG, Black,
600V, THW, by the foot, Code Approved, 4/0-X-FLEX-B
|440-0026||Quick Cable, Magna Lug, 4/0 Straight Lug, 3/8”,
Qty, 1, 6440-F
|440-0083||Quick Cable, Heat Shrink, 1/0-250MCM, Black,
Qty. 1, UL Listed, 5615-051B
|440-0084||Quick Cable, Heat Shrink, 1/0-250MCM, Red,
Qty. 1, UL Listed, 5616-051R
|440-0178||MK Battery, Unigy II, 4V, 2 Cell Module, 2424Ah @ 24hr, Interlock, 2AVR125-33 IL
*** Sealed battery pack above to be configured w/ two 48v
strings per cluster (there’s 4 clusters). Will deliver approx.
2.5 days of power use. Life expectancy is 15-20 years.
|Estimated Shipping Cost||10,987.23|
As part of our self-sufficient and self-propagating teacher/demonstration communities, villages, and cities strategy our goal is to make duplication of a solar array like this as easy as possible through:
Electric power requirements (see below) have been estimated by JP Novak of Build Native.com. The above system was then designed by Doug Pratt applying his 27 years of solar design and installation experience to confirm these estimates (below) seem reasonable. Estimating how people will use power in advance is always a guessing game and our initial guess missed the mark when we A) realized rocket mass heaters would not be a viable option for the earthbag village and B) that heating the Duplicable City Center and operating the large-scale kitchen was going to be far more energy intensive than we originally expected.
So now we are redesigning the above system with precision and all the new details of our ongoing development progress. Also, it is important to state that humans are nothing if not variable and we anticipate that this system will almost certainly require some fine-tuning even though we are doing our best to account for even the most minute details. We also anticipate that our group will learn from experience and probably become more energy aware and conservative with time. To help us gather data and fine-tune our process as part of our open source sharing, we will be using simple metering on all homes, the Duplicable City Center, and the aquaponics systems. By doing this we will be able to identify “energy hogs” and share this data, our solutions, and the objective energy saving results of our solutions.
The total electrical use for the earthbag village, aquaponics, and the Duplicable City Center, on a yearly average, was initially estimated to be 282.5 kWh per day. This is the figure used to size the solar electric system. In addition, all the AC appliances that were likely to be on simultaneously were totaled up. These included a percentage of lights, laptops, microwaves in the homes, along with all the aquaponics hardware, and most of the kitchen and community center lighting and hardware (including the hot tub). This max AC surge was about 76 kW and was the figure used to size the inverter pack.
An Updated Version of this Information is Coming
|Pod 1 Power Requirements (72 units)|
|Aquaponics Power Requirements|
|Duplicable Center City Hub Power Requirements|
|(12 Suites/170 capacity dining room/3 Conference Areas/Laundry/Kitchen/Library)|
|Maytag Washer (Maxima 4.3 cuft)||200||2.5||5||2.5||75|
|Maytag Dryer (Maxima 7.4 cuft)||1000||2.5||5||12.5||375|
|Refrigerator (40 cuft)||1000||6||2||12||360|
|Walk-in Freezer (8′ x 6′ x 8′)||0||2280|
|Walk-in Cooler (10′ x 20′ x 8′)||0||1600|
|Stand Mixer (30 qt.)||2000||1||1||2||60|
|Griddle (3′ x 2′)||1500||2||1||3||90|
Okay, so how do we go from kWh per day to PV arrays on the ground, and battery sizing, and inverter sizing, etc.? Here’s how Doug described it for us:
Looking at available sunlight for the property: The National Renewable Energy Labs (NREL) went out and measured sunlight availability for several hundred sites across the U.S., and they did it for 30 years. 1960 thru 1990. So we’ve got a nice average. This is the “NREL Redbook”, and is the standard source for estimating sunlight availability at any point in the U.S., for any time of year. For our location we have a yearly average of 5.9 hrs of peak sun per day. Peak sun? What’s that? That’s the scientific definition of full sunlight on the Earth’s surface. A “full sun” is defined as 1,000 watts per square meter. Now it’s immediately apparent that’s an impossibly round figure. And you’re right. Reality on the ground varies widely depending on humidity, altitude, sun angle, and a host of other variables called “the weather.” What NREL has done for us is to take all the hours of sunlight on a particular site and condense it down, as if all the hours were at perfect solar noon – 5.9 peak hours in this case. Which is pretty handy, because PV modules are rated to produce a certain amount of power at “full sun.” If we know a site averages a certain number of peak hours of sunlight, we can closely estimate how much power a given PV array will deliver. Now, a warning here, we’re talking about the weather. And it varies from year to year. In fact the NREL data clearly demonstrates that it varies by plus or minus 9% yearly. So it’s not worth getting too hyper-sensitive to accuracy with our system sizing, as there’s bound to be yearly variations.
5.9 hours is the yearly average sun for our location. In December, at the lowest, it drops to 4.4 hours, which is still pretty good as solar sites go. For a December site, it’s excellent, and we’re going to use the 4.4 hour figure for PV system sizing. Now we know how many kWh per day your complex needs, we know what the average sun is going to be in December, what’s left is system efficiency. How much is lost to wiring, dusty modules, batteries, inverters, etc? Real world measured efficiency for battery-based systems ranges from 50% to 70%. Since much of the energy in this system will be used during daylight hours and will not need to be stored in batteries, I’m giving this system a fairly high 65% efficiency rating. This is completely seat of the pants estimation based on experience with large battery- based systems.
So we’ve got a 282.5 kWh nut to crack with 4.4 hours of peak sun and a 65% efficient collection and delivery system.
282.5 kWh / 4.4hrs / 65% = 98.77 kW of PV required. How many of what PV module is left until later, probably until right before purchase as prices and module brands have been shifting rapidly.
Batteries are the largest expense for the system. Lead prices just keep rising as the world becomes more industrialized. Lead-acid batteries still represent the best buy for remote systems. (And before you ask, lithium-ion batteries are still at least 4-5 times more expensive, and haven’t proved they’ll last longer than lead-acid. Who hasn’t had problems with phone or laptop batteries?)
When sizing off-grid battery packs we usually aim for about 2 to 3 days worth of storage capacity. Less capacity means the batteries get cycled deeply on a day to day basis, which isn’t good for life expectancy. More capacity raises the cost to where it’s cheaper to start the backup generator to meet the occasional shortfall.
Batteries are sized by amp-hours rather than watt-hours, so we have to divide our watt-hour figure by the battery voltage – 48-volt in this case. (If you remember your high school physics, watts divided by volts equals amps. Or volts times amps equals watts.) We also have to factor in how deeply we’re willing to cycle our batteries. The true deep-cycle batteries we’ll be using will tolerate cycles down to 80% depth of discharge (DOD), but again, deep cycles aren’t good for life expectancy, so we’re going to draw the line at 70% DOD. Considering the high quality of the Unigy II batteries we’ll be using, along with reasonable cycle depth, this battery pack should enjoy a 15 to 20 year life expectancy. By which point lithium-ion batteries may be a better choice. That’s a bridge to cross when we get there.
282,500 watt-hours x 2.5 days / 48 volt / 70% = 21,019 amp-hours @ 48v. This is one honkin’ BIG battery! To help make it more manageable, we’re going to use an SMA Sunny Island Multi-Cluster inverter package which divides the inverters up into four separate nodes, with each node having its own battery pack. And that brings us to Inverter Sizing next.
Doug chose the Sunny Island Multi-Cluster inverter package for several reasons. It’s highly reliable and adaptable German engineering at its best. It consists of 12 individual Sunny Island 6kW inverters wired as four groups of 3 inverters each. So 12 x 6kW = 72kW, very close to the max AC surge requirement we estimated earlier. (Each 6kW Sunny Island can deliver 8.4kW for 1 minute, or 11.0kW for 3 seconds for true surges.) Each node of 3 inverters will cover the A, B, and C phases of your 208vac 3-phase system. As power demand increases, the Multi-Cluster will activate more nodes as needed. So we won’t have a lot of inverter capacity turned on, using power, and just waiting for something to happen. Capacity will only get turned on as needed. Each node has its own battery pack, which will make the individual packs more manageable. And if any one inverter or battery pack needs service, that node can be shut down, while the rest of the system will still operate normally. Also, the Sunny Island system uses conventional high-voltage grid-tie inverters to process the incoming PV power. So transmission from PV arrays hundreds of feet away are much less of a problem.
While this system is designed to be largely automatic and self-sustaining, there will be one or more designated maintenance and service personnel for the community. This person will be in charge of system operations, and trained to be familiar and very comfortable with the Sunny Island system. In addition, a great deal of system automation is possible with the Sunny Islands. As battery state of charge drops to critical levels, the Island can initiate start-up of backup generators, and/or shut down selected loads (the hot tub for instance). Routine maintenance includes cleaning PV arrays, snugging up battery cables, and monitoring the Multi-Cluster for any warnings or problems. For this reason, someone dependable and knowledgeable will be “in charge” of the system at all times.
Completely off-grid energy production in remote locations requires planning and a detailed phase-in process if the goal is to build as effectively and efficiently as possible. One Community is open source sharing our design process and rational as a foundation of establishing self-sufficient and self-propagating teacher/demonstration communities, villages, and cities. We will evolve this page with more details as they develop. These details will eventually include complete installation tutorials, maintenance details, purchase order specifics, and more.
Q: How are the generators sized?
Generators are sized using the maximum continuous wattage (power) that they can reliably create. If, when every device is turned on and running at maximum, the power draw is 95 kW then we select a 100 kW generator. Most of the time the power draw on the generator will be much less than the maximum load.
Q: How is the system sized?
The energy system will always be designed for the worst-case, maximum load. This would include sizing wires, fuses, and busses to handle every possible device and appliance turned on at once. Even though this is a very unlikely scenario, it ensures that the system will always work within its safe limits.
Q: In what case would the generators activate?
In the beginning we will use the generators for many different activities, but as the project adds sustainable energy sources to the property the generators will be phased-out in favor of the more sustainable options. However, we will keep the generators on site, in running order and fueled in case of a fault in any part of the energy management system. Or to as make-up energy for the system.
Q: What happens in the case of a massive battery fault?
In this scenario the battery banks are damaged or in some way inhibited from providing the stored power back to the energy manager. As the energy manager senses the drop (or stop) of battery power it will send a “Start” command to the backup generators causing them to start, reach working RPM, and sync into the energy manager’s grid. During this time the total load of the project less the total amount being created by sustainable means at that instant would be placed on the generators. They would run until battery storage was back online or the sustainable systems were creating enough power to cover the current load.
Q: What happens when there is not enough power to charge the batteries? (Cloudy Week Scenario)
Sometimes there will be a deficit of energy created in the day (solar, wind…etc.) and the remaining energy needed will have to be “made up.” The energy manager will run one or more generators at the most fuel efficient load for as long as it takes to charge the system. Once charged, the energy manager will automatically shut down the generators. In times of low light due to atmospheric disturbances this could become a daily occurrence to meet the forecasted demands on the system.
An example would be the energy manager calculating the amount of energy in storage and if the stored power does not meet the energy needs of the system for the next 24 hours the generators would run after the solar cycle (evening) to “top off” the batteries for the following day.
Q: What happens in the case of an energy manager malfunction?
In the case that the energy manager fails to operate or detects a fault, the system would go under total generator control. Because improper battery management can cause catastrophic damage, it is safer to allow the generators to take on the entire load of the system and remain in that state until the energy manager fault is discovered and fixed.
Q: How does the system change in an emergency scenario?
As a fault is detected in the system the energy manager, programed in advance, will compensate by utilizing the different power storage and production equipment options that are connected to the system.
Normal management would be the phasing in and out of sustainable power sources as they come online. However, in the event that a subsystem fails in such a way that could be damaging the entire system, like a short circuit or an unexpected voltage spike, the manager will remove the offending device from the system and rely on other sources. Mechanical systems (fuses, breakers) will also be in place in the case of a very sudden change in voltages that could be too quick for the manager to compensate, such as a lightning strike or short.
Q: What are the fail-safe measures?
Whenever possible all parts of the system will be designed to fail in a way that provides the safest possible scenario for the rest of the system. Whenever possible the system will also continue to provide power. This said, there could still be times where a catastrophic failure fail-safe would be to cut power completely. The details of this system of fail-safes would depend on the environment in which the system is placed and it’s particular construction and components, so at this time there are no definitive plans.
Q: What systems would be active in a power emergency?
In a power emergency only essential systems should be left on. The following factors would determine which systems are essential:
To help put the energy needs of different systems in different situations into perspective, here is a chart showing how much specific components of One Community will contribute to peak wattage needs:
Now compare this to this chart that shows how much specific components of One Community will contribute to total energy needs:
The point of these two charts is to show that components like the heat pump, dryer, and water heaters draw the most power from the perspective of total daily needs because they will be running consistently. Individual heaters, the boiler/water heaters, dryer, and parabolic heaters are the top contributors to peak wattage (energy spikes) because they draw a lot of power at one time. The general trend is still that those items high on one chart are also high on the other chart, but the details will vary and this can be extremely helpful to understand and consider in emergency power situations. Also, to conserve power, the hot tub (a huge energy consumer) has been designated as an item to be used only when surplus energy is available (like in the summer months).
Q: How much bio-diesel will you need?
The fuel source should be sized to provide enough for the running of the generator to meet team power needs for at least the amount of time the team is planning on this phase multiplied by a safety factor of 1.2. For the Landing Party of 20 people we assume that we will be using roughly 4.2 kWh/day per person (from Pod 1 per capita energy consumption). Over the course of the day we can assume that we run the generator for 5 hours continuously per day meaning that during that 5 hours the generator is running at 16.8 kW or 16.8%. Using the graph in the related section above, we find that the 100 kW generator will consume 3.34 gallons per hour at that load. Multiplying the number of hours by the fuel consumption rate gives us 16.7 gallons/day times our safety factor of 1.2 gives us a final value of 20 gallons per day for the average day.
Fuel storage on site would then be divided by 20 gallons per day to give us the number of days the fuel source can sustain the party. The 100 kW generator with the 250 gallon base tank would last the party roughly 12.5 days without filling. Fuel for an entire month would be 620 gallons total. At today’s prices that would come to roughly $2,480 per month for normal or $2,000 for farm diesel.
Q: What are the benefits of bladder storage for fuel?
Storing fuel in a large bladder is by far the most economical way to store the biodiesel used by the generators. However, bladders are flimsy and easily punctured. They cannot be buried either, so they would have to sit on the ground somewhere protected from heat-sources, and sharp objects.
Q: What are the benefits of tank storage for fuel?
While Tanks are more expensive than bladders, they can be buried to keep them away from heat sources and punctures. Larger tanks would take a large piece of land-moving equipment to place underground.
Q: How long will the batteries take to drain?
Very simply, batteries are rated with their voltage (average) and Amp-Hours. A 50 A-hr 12-volt car battery will provide 1 amp at 12 volts for 50 hours, or 50 amps for 1 hour, or 25 amps for 2 hours, etc. This is the principle used to size the batteries needed on the property. Knowing that we need to provide a certain amount of power (lets say 5 kW) over a certain amount of time (2.5 days = 60 hours) we can start to calculate the batteries needed.
Typical high-voltage batteries can be around 48 volts. Knowing that Volts X Amps = Watts, we can determine the number of amp hours needed:
Since we need that over the course of 60 hours:
If the largest size of battery we can find is 1000 A-H, then we would have to buy 7 of them to cover this draw for 2.5 days.
As with all engineering calculations, the largest (predicted) average power drain will be taken into account to build in a buffer to our system.
Q: Why not use the grid?
Most solar power systems in the United States (and other first-world countries) use the grid as a backup source and storage system. When the system is producing more power than is needed the system provides power to the public grid for others to use. The electric company measures this and creates a credit (in $$) to the person’s account with them. In times of decreased solar power production the credits are used to pay for the remaining energy needed that is not provided by the solar array. If the system is sized correctly the balance over the course of the year will be $0.
Why don’t we do this? There are two primary reasons: