- Lighting - LED Lighting. Not really an issue. Already low power.
- Fridge - 300W Refridgerator -> 60W Low-voltage 12V car fridge (smaller size), no freezer.
- Stove/kettle – 1200W Electric stove -> 144W Low-voltage 12V car cooker. Heats things up to 300F – can cook rice, etc.
- Air Heating - 5600W Central heating (oil furnace) -> 150W Low-voltage 12V car heater
- Air Cooling - 1400W Air Conditioner -> 45W Low-power evaporative cooler
- Transport - Car -> Electric skateboard or ebike (though I prefer a bike to stay in shape).
- Communication – Laptop, Phone. Not really an issue. Already low power.
- Hot water tank - No alternatives yet if we want hot showers, unfortunately.
- Dishwasher - Wash dishes by hand. Sorry y’all.
- Washer/dryer - Hand wash and hang dry feasible?
What can the system run? Off-grid life = low power devices. | 17 Sep 2017
A lot of questions we receive here are as to what you can charge and how far the energy will reach. I thought this would be worth a separate, more in-depth analysis. The findings from this article are now in the updated Parts List
What adjustments would living off a single 420Wh system require of your lifestyle? Worst energy culprits in my household are roughly in order of energy use: hot water tank for showers, stove/kettle, transportation, air heating, air cooling, fridge, dishwasher, washer/dryer, lighting. Living off 420wh a day requires replacing the culprits with lower-power parts (often intended for car, RV or marine use). At this point this project becomes very similar to the original inspiration for this article - Robin Rhineharts How I gave up alternating current (Robin Rhinehart is the founder of Soylent). Replacing high-energy AC appliances with low-energy DC ones to stay within the 420Wh “budget”.
Low-power thought experiment:
Low-power devices you can run off a single 420Wh system:
|LED Light||Fridge||Stove/Kettle||Air Heating||Air Cooling||Transport||Communication|
|LED lights||Car fridge||Car cooker||Car heater||Evap. cooler||E-Skateboard (/E-Bike)||MacBook Air, iPhone|
|2 lights * 4W * 5h||60W * 7h||144W * 1h||2h * 150W||9h * 45W||1 charge||1 charge each|
See the actual components for this experiment here. Note that almost all components above run on DC, so it’s technically feasible to make the cheaper DC-only system from the aforementioned parts page.
High-power devices in my household that have no low-power replacement yet:
But what if we’re not constrained to just 420Wh off a single system? This is where the componentization of the system comes in handy – we can just keep adding systems until our (reduced) power needs are covered by the panel+storage systems. How many systems would we need to run all of the devices above?
The total load for all the components in the theoretical off-grid apartment above is 1510Wh (or 1.51kWh). We’d need 4 systems to load all of the components every day and be completely off-grid in our apartment (or glamping or post-hurricane). Some compromises would be necessary like cooking with gas and washing by hand. The total cost would be around $800 (see parts list) – and payback would be around 8.5 years if we used it every day based on Californian electricity prices (@11c/kWh), or 5 years based on 20c/kWh in NY.
Burning Man 2017 Update | 06 Sep 2017
We found numerous burners who had built, customized and improved on the solar self-sufficiency system at Burning Man in Nevada. They were being used to run phones, fans, swamp coolers and lights.
Attached Sean’s great system:
The panel is mounted on top of the car at a fixed angle. The cables lead to back to the box next to the tent.
Next to the tent, the toolbox contains the battery, inverter and controller. Next to it is a swamp cooler and a cable leading into his tent (AC extension cable from the inverter in the box) powering another fan, chargers and lights.
Sean’s running a great modified system – DC power goes to the swamp cooler’s fan, the battery is laid into the tool tray. Plenty of extra space in this toolbox, which protects the system from dust and the sun.
Sean listed the main three reasons he decided to build his own system vs. bringing a diesel generator:
* No Fuel Required * No Noise * Compact
“A green (his words) device with enough wattage to power a DC swamp cooler”. He usually got 6 hours into the night before the battery was drained, but at that moment the sun came up and started generating energy again to power the swamp cooler.
We’re going to add a box to the recommended kit, to give it a more rugged and finished look for outdoors and festival use.
The Problem & a possible solution | 16 Aug 2017
Apartment renters need the landlord’s permission to install anything on their rooftops. This makes installing solar difficult for people who rent. Because most of the world lives in urbanized areas where renting is common, I think this is a problem standing in the way of solar adoption.
An additional speed bump is the complexity of installing solar: regulation around net-metering. Grid-tied systems. Installation permits (even if you do own your property). Getting quotes from different installers. Solar financing. All complex processes inherited from the construction industry which slow down mass private adoption of renewables.
In the following I attempt to bypass both these problems by building a standalone solar power plant on my windowsill with off-the-shelf Amazon parts, and discuss the pros and cons of this approach to solar.
A possible solution
A windowsill solar system bought off Amazon solves both problems at once: Renters don’t need permission from their landlords to place things on their windowsill and rooftops if it’s not altering the building, and it’s a one-click Amazon purchase with no regulation as long as it’s not tied to the grid (which mine is designed not to be). Two birds with one stone. This makes the solar buying process more like buying a consumer electronic.
Questions remain. Can this system make any meaningful energy? Does it make financial sense?
Learnings So Far | 11 Aug 2017
This project started with a simple idea: What if energy generation was a consumer electronic you could order off Amazon? I’ve learned that basic electrical knowledge and a little assembly bring us very close to this ideal: Self-contained renewable lighting and charging is achieved with a simple setup off Amazon.
Unless you live on an RV or a boat it doesn’t make financial sense yet (see epilogue #1). But if prices come down a little more (what a difference the last year made!) or manufacturing gets a bit more resource-efficient the scales could tip and this could be a green and fiscally sensible solution (see epilogue #2). And some time in the next decade this great little DIY system that can function as a back-up system today (see epilogue #3) could become a viable consumer electronic: a cheap personal power plant for urban renters.
What if autonomous electric generation could be added room by room to a household (like window A/C units)? We could outfit all 7 rooms of my (shared) household for around $1400 with this system today. Because the kitchen and bathrooms have way higher energy usages (fridge, stove, water heater) than the other rooms, a more sophisticated system could mesh the batteries together (wirelessly?) to create a stronger system that sends power to the rooms that need it most. This system could also discharge the batteries systematically as the price of grid power changes and the sun moves around the house.
Solar as a modular consumer electronic — like air conditioning and satellite dishes? If we look to the car, the smartphone, the window A/C unit — these devices spread like wildfire across the globe because they were off-the-shelf products that required no configuration but great benefits. Identical appliances were churned out at an industrial scale for a global audience. They were “plug n play”. Plug n play solar has been around for a while, but has never taken off (probably because behind-the-meter power is still sketchy and poorly understood). The potential for plug n play solar is huge — it could mean cheap, zero-configuration solar energy spreading to consumers at the pace of the smartphone, the car or air-conditioning. This could be a cool Kickstarter project in the future… or a just fun DIY project today.
Tech Specs | 15 Jun 2017
Polychristalline Solar Panel Size: 39.8 x 1.2 x 26.6 inches Weight: 19.6 pounds Voltage: 12V DC Max power rating: 100W Max amperage: 8.3A Inverter Max power rating: 150W (it'll turn off if you use more than this, but a 300W version is $6 more) Voltage: 12V DC in, 110V AC out Only DC 12V, NOT for DC 24V USB Output: 5V/1+2.1A (5W and 10.5W respectively) Solar controller Voltage: 12V/24V Ports: 2x USB, 1x DC in, 1x DC out Charge Current: 20A Discharge Current: 20A Max in: 20A * 12V = 240W Max out: 20A * 12V = 240W USB Output: 5V/3A (15W) each Type: PWM Weight: 0.25 pounds Size: 5.9 x 3 x 1.4in Will upgrade to a USB-C version when available Marine lead-acid battery (Deep Cycle) Voltage: 12V DC Storage Capacity: 0.42Kwh, 35Ah Size: 6.5 x 7.7 x 5.1 in Weight: 25 pounds Cables (aka "Tender" or "B.O.S.") Alligator Clips (for connecting the battery to the solar controller) 20Ft Extension Cable (MC4 12AWG, for connecting the solar panel to the solar controller)
The How-To Build Guide | 20 May 2017
My goal is to take care of the energy needs for just my bedroom. 4 main components are all we need to achieve this: A solar panel to collect, a battery to store, an inverter to convert the direct current to alternating current, and a “charge controller” to balance the three other components. I’m using bargain-basement parts intended for RV, marine & car usage which keeps my system cheap and mobile. The main components as found on Amazon are above. Anyone looking to build a similar system themselves can view the full component list here (tweet your build @gridlesskits, how it went and what we can improve! We’ll repost – and we’d love to know!).
I ordered the system on July 2nd, and with ground shipping the PV panel arrived July 11th from Canada, and the battery, wiring, controller and inverter arrived July 15th from Amazon USA.
Hopefully you can adapt my system to your spatial situation pretty easily:
Step 1 Cut and lay bare the end of the battery & inverter wires (battery disconnected, please). The panel’s wires are already bare on one end. Do a dry run connecting battery, inverter and panel to the controller — it should look like above.
Step 2 Detach the panel wires again and place the panel on the rooftop or wherever you get the most sunlight (…garden …balcony …). Attach the panel to something: I zip-tied the back of the panel to a cable which I fastened on both ends around sturdy roof pipes…
…and run the power lines back to your apartment (drop down the facade and into the window in my case).
Step 3 Assemble the solar controller, inverter and battery into a tighter package. Re-clamp the wire from the panel to the solar controller and close the window. It should look as above. The charge begins!
In the evening, turn on the inverter. My lamp, computer, tablet & phone are all being powered simultaneously here on the day’s solar charge! Self sufficiency achieved?
Trying to live self sufficiently in my room | 20 Mar 2017
In San Francisco we get 4.26 hours of usable sunshine a day (or 1156 hours a year) according to Google Sunroof. My battery holds 420Wh (12V x 35Ah), and should be filled once a day without any shading. Actual production is an average 350Wh/day on the rooftop with real-world shading and loss.
Daily Power Production: Theoretical: 4.26 sun hours/d * 100W solar = 426Wh/day Actual: 350Wh/day Daily Power Needs: 54Wh Macbook Air 13-Inch (one charge a day) 8Wh iPhone battery (one charge a day) 20Wh Light (4W LED x 5h) 300Wh Space Heater (150W x 2h – our SF house has no heating) ___________ Total: 82Wh energy need per day in room (up to 382Wh)`
This should be easily met by the solar system. I turn the inverter on when I get home to use AC lights and charge the Macbook through the power brick, and turn it off before I go to bed to avoid energy drain. My phone’s USB (which is direct current) can charge all night straight through the solar controller itself (which has USB ports) and doesn’t require the inverter. My laptop is a DC device and could be charged straight off the 12V battery, but I found it easier to just charge it with the AC power brick through the inverter.
My traditional AC lamp is a non-optimized part of the system— I could get DC lights that run off USB to avoid inverting that energy, but have not done so thus far and prefer to just use the cute little thing. When I go to bed I’ve usually used around 30% of the energy anyway— I wish I could run a water heater, heating or fridge off this system to use the excess 270Wh of the daily energy production.
Financial Payback & Embodied Energy | 12 Feb 2017
How long until it saves me money? The reason this system is so simple is because it doesn’t tie in to your apartment’s behind-the-meter electrical grid. This means the system is clean, but it also doesn’t feed into electrical heavyweights like your water heater, refrigerator and washer/dryer. It does charge anything you plug into it though. So can the system save me money? Back of the envelope:
Financial payback period for 100W system System cost : $211 on Amazon at time of writing Yearly energy creation: 365d * 4.26hsun/d * 100W = 155’490Wh/y Yearly value creation: 155kWh/y * 15.34c/kWh = $24/y energy created 100W system payback period: $211 / $24 = 8.5 years until payback
The financial payback of the system is 9 years including battery, which is in line with many rooftop systems but doesn’t include servicing. This could be reduced to 6.5 years by adding a second 100W solar panel:
Payback period for 200W system 200W System cost: roughly $300 on Amazon at time of writing Yearly energy creation: 365d * 4.26hsun/d * 100W = 310’980Wh/y Yearly value creation: 311kWh/y * 15c/kWh = $48/y energy created 200W system payback period: $300 / $48 = 6.5 years until payback
Note however that after 8 years of daily use the lead-acid deep discharge battery will be spent, which I’m not taking into account here. Either way you cut it, this is not a money saving machine. Energy prices are just too low.
How green is it?
Does it have an impact on my CO2 footprint? Back of the envelope:
Production footprint PV multicristalline: 4200kWhee/kW  * 0.1kW = 420kWh embodied energy Production footprint lead-acid battery: 321kWhee/kWh  * 0.5kWh = 161kWh embodied energy Total Footprint: 581kWh Annual energy production system: 155kWh/y Payback period: 581kWh / 155kWh/y = 4+ year footprint payback  http://renew.org.au/articles/energy-flows-how-green-is-my-solar/
An eventual product would use Lithium-Ion batteries once they come down in price, which have a way better energy footprint. Lead-acid batteries are used for now because they’re cheap. So no, we’re not saving any CO2 emissions here until after 4 years — not a green machine.
Energy independence and resilience In case of brownouts or blackouts, this would be a helpful way of wirelessly charging communications devices without the grid. A 200W system could even keep a small 60W, 12V refrigerator cool enough to conserve food (14hours of operation/day, cooling down 32 degrees below ambient temp). If energy prices increase (double? triple?) due to unforeseen events in the future, the financial perspective may even make sense with payback periods decreasing to four or even 2.8 years for the 100W system or for the 200W system to 3 years or 2 years, respectively. At under 2 years payback period, we’d be in similar consumer territory to 2-year phone contracts. Let’s hope components continue to get cheaper! (or energy prices increase — but I’d rather not hope for that)