Solar In A Box

The Pitch

Do you own a flat screen TV? If you live in America and are middle class, there is a pretty good chance you do.

Do you own a solar power system? Probably not.

In 2006, Americans purchased more than 17 million flat screen TVs. During that same time, we bought less less than 10,000 residential solar power systems.

I don't think this is because Americans care more about TV than the environment. I think that most Americans want to do something to reduce their impact on the environment, especially if it would save them money.

I think it is because flat screen TV are easy and solar power systems are hard.

Consumers can easily walk into a Wal-Mart store and purchase a flat screen TV and bring it home and plug it in.

Solar power systems today require a huge investment of time, effort, and money to install. If you could buy an inexpensive solar power system at Wal-Mart and bring it home and plug it in, I think that millions of Americans would.

The Concept

Create an off-the-shelf renewable electricity generation system that you can buy at the store, bring home, and plug in. The components of the system are simple, cheap, and modular.

The Hub

A 200 Watt hub with one outlet and one solar panel. Perfect for powering a desktop computer.

The hub is the base of the system. You plug the hub into a normal wall outlet and then you connect a load (appliance, computer, lights) into the hub. Both connections use normal household 3-prong plugs. You also connect the solar panel into a special jack on the hub. When the sun is shining, the hub converts the DC energy coming from the solar panel into AC energy that your stuff can use. When the sun is not making enough power for your load (because it is cloudy or nighttime), the hub seamlessly supplies the extra power from your house mains so you always get continuous power.

The hub above has a display that shows the amount of power the load is using and the amount of power that is being supplied by the solar panels.

A 1000 Watt hub with 6 outlets and connections for 4 solar panels. This could support a small air conditioner or several appliances.

Hubs come in many different sizes from 200 Watts to 2,000 Watts. Bigger hubs have multiple energy source jacks, so you can buy extra panels and plug them in at anytime to expand the system.

The hub is in constant digital communication with the connected power sources. The communication link runs over the same wires that carry the power. Because the hub is able to read information from the connected solar panel, it can make adjustments based on what size and type of panel attached and run at maximum efficiency. If the communication link is ever broken because the wires are damaged or disconnected, the power source instantly stops sending power down the lines. This makes the system fail-safe.

Power Sources

A Solar-In-A-Box solar panel is just a standard solar panel with the addition of an inexpensive module that makes it compatible with the system. This module is responsible for maintaining the communication link with the attached hub. When a panel is first connected, the module tells the hub information that the hub needs to operate the panel at its maximum efficiency. Then the hub sends a signal to module telling it to start sending power down the connection. The module only sends power down the wire when it is connected to a functioning hub.

But as a consumer, you do not need to know about any of these details. You'd just buy any compatible power source and plug it in to any hub.

These modules could also easily be incorporated into any power source cable of supplying DC power, making that source able to plug directly into a hub. This would include a variety of different sizes and types of solar panels and also windmills, small hydroelectric turbines, even a stationary bike with a generator.

FAQ

Q: What makes a Solar-In-A-Box hub different from existing solar power inverters?

A: There are two types of solar inverters available today - grid-tied and non-grid-tied.

Grid-tied inverters take the electricity generated by the solar panels and feed it back into the electrical grid. This is a very complicated process because the inverter must be exactly in sync with the electrical power being generated by the local utility. The grid-tied inverter must also meet very stringent regulatory requirements because it could potentially effect a large number of people. The existing grid-tied inverters are fantastically engineered to meet all these difficult requirements, but all this extra functionality makes them expensive to produce. Because they feed power backwards, they must be hard-wired into a dedicated breaker on your electrical system. This usually has to be done by a qualified electrician.

Non-grid-tied inverters are not attached to the grid at all so they are much simpler and cheaper than grid-tied inverters. Because they are not connected to the grid, they typically must rely on batteries to supply power when a cloud goes by or at night. Batteries are big and expensive and inefficient.

The Solar-In-A-Box hub is the best of both worlds. Because it only sends power to the directly connected load and never back into the grid, it does not need all the extra complication that a grid-tied inverter needs. When the solar panels are not supplying electricity, the hub can draw power from the grid as needed, avoiding the need for batteries.

Q: Is this net metering?

A: No. With net metering, when you make more power than you need you send the excess power back to the grid and that turns your meter backwards. Then, some other time when you need more power than you are generating (at night) you draw from the grid and your meter runs forward again.

With Solar-In-A-Box, you never send electricity back into the grid. You use any available solar power when it is generated, and use grid power when solar power is not available. This means that Solar-In-A-Box typically does not reduce the amount of electricity you buy at night, but only during the day when the sun is shinning (unless you also plug a windmill power source into your hub).

Q: Is this better than net metering?

A: Theoretically, net metering is perfect - if you make more solar power than you can use, you can share it with everyone else on the grid. This typically happens on hot, sunny days which is exactly when the grid really needs some extra power. Even better, the power you are making is put on the edge of the grid where you and your neighbors live, so it doesn't have to travel over long transmission lines to get to where it is needed most (lots of power is lost during transmission). Then, later that night when you need so power to watch TV, you can take back some of what you gave at a time when there is not as much demand on the grid.

Unfortunately, there are some complications. The biggest one is that net metering depends on you sending power to your local electric company. This means dealing with lots of regulation and bureaucracy. In practice, this makes grid-tied solar systems difficult and expensive to install. You are not even allowed to do net metering in some states. I wish it were not true, but it is- and there is no realistic way to change it in the near future.

Because Solar-In-Box never sends power back into the electric grid, the whole system works just like any other electrical product you'd connect to your electric company. There are no special regulations or agreements, you just plug it in.

I think the concept of net metering would be the cure to all our woes in an ideal world. Alas, we need practical solutions that can actually work in the world we live in today. Solar-in-a-box is all about doing something now that has a real and practical impact.

Q: What happens if my solar panels are making more power than my load is using?

A: Because the Solar-In-A-Box hub can not send excess back into the grid, any solar power that is not used is lost. To make sure you efficiently use all the solar power that is being generated, you need to plug in appropriate sized loads into the hub. Ideally, you'd want to to plug in enough stuff to a hub to use slightly more electricity than the solar panels can produce, this way you'll always use all the power generated. Loads that use a constant amount of power during times when the sun is shining are perfect (think computers, air conditioners). You don't get any benefit by connecting something that you only use at night.

Q: Why hasn't anyone done this before?

A: I don't know. Maybe they have. But since I can't find any Solar-In-A-Box systems at my local Walmart, I have to assume that if they did try it, they didn't succeed.

Q: Do you have a patent for this idea?

A: No, and I don't want to. I'd be very happy if lots of people started making their own Solar-In-A-Box compatible components. The competition would drive down prices, and different manufactures could offer a wide range of sizes and features.

APC might want to make a hub with a built-in battery so it would work even during a power failure. Dell might want to make a hub that was built into a computer where the power supply would normally go so the computer could automatically wake up when there was extra power and do power intensive tasks. GE could build a hub into a refrigerator that would make ice when there was free power available.

There are lots of innovation opportunities for power source manufacturers too. While Sharp might make a large but inexpensive standard solar panel that plugs into a hub, Green And Gold might want to produce a Solar-In-Box version of their hyper-efficient and space-saving SunCube DC for apartment dwellers who have small south-facing terraces. Southwest Windpower could even release a Solar-In-A-Box compatible windmill that would work for people with more wind than sun. Heck, you could even connect a micro-turbine to your hub and run the dehumidifier in your basement off of power from the stream out back.

All of these components would work seamlessly together, so you could buy exactly what you need and just plug it in.

Q: But with Solar-In-A-Box, people are still using power from the gird. Shouldn't we be getting people off the grid?

A: Solar-In-A-Box is about finding a practical and realistic solution to reduce our environmental impact today. The goal is to make something that normal people can actually afford, buy, and use now to make a difference.

It turns out that you do not need to move everyone off the gird to make a huge difference in our environmental impact. Sunny days is when demand on the grid peaks, and this is when power companies are forced to use the worse polution producing sources for power. By just reducing the demand at these peak times a little, you can prevent huge amounts of pollution from being produced. By making Solar-In-A-Box cheap and easy, you make it possible for huge numbers of people to participate. Even if only a small percentage of us could use Solar-In-A-Box to cut our peak demand by a small amount, the net impact would be huge.

Also, because the total installed cost of a Solar-In-A-Box system can potentially be so much lower than a grid tied system, people will be able to save more money overall that they would with a grid-tied system, and many, many more people will be able to do so since the barriers (cost, effort) are so much lower.

Q: How do you mount the solar panels?

It is important the the mounting systems do not require any permits to set up. They should also be easy and not require any skill or tools more than, say, setting up a piece of lawn furniture.

The standard solar panel would come with a simple aluminum-tube frame that you could just put down on any sunny spot in your yard. It would come with a handy flat cable that could run in though any window or door. You can move the frame around to get the best sun exposure from season to season, or just to mow the grass under it. It would also have an easy way to adjust the angle of the panel so you could change a few times a year as the sun rises and falls in the sky.

There could also be a window mount that would hang a panel from a window still. The window would close on it to secure it, similarly to the way you mount an air conditioner in a window. It would have an integrated cable to get the power from the attached panel into the room.

I'm sure that many, many people will come up with many more innovative ways to mount the solar panels that do not require permits. The best will be for sale at WalMart in the Solar-In-A-Box Accessories section.

Q: Where can I buy a Solar-In-A-Box system?

A: You can't but one- yet. All of above pictures are (crude) photo-shopped mock ups of what I think a system might look like. For now this is just an idea. I'm hopping that I can get enough people interested that it can become a reality.

The technology is ready. The electronics inside a hub are similar to what you'd find inside a UPS. A UPS converts the AC power from the wall into DC to charge its batteries, then converts the DC from the batteries back into AC to power the outlets. Replace the batteries with a connection for a solar panel and add some software to make it more efficient and you have a hub. You can get 500 Watt consumer UPS for as little as $59 today. A 500 Watt hub should cost about the same and be smaller because there are no batteries inside. One of the existing UPS manufactures would be a perfect candidate for making hubs.

The module that attaches to the back of the solar panel (or any power source) would contain a tiny microcomputer, some components to handle the communications link over the connection. and a switch for controlling the power flow though the wire. All these parts are cheap and readily available today. My guess is that this module would only add between $1 and $10 to the cost of the power source depending on the size of the power source and the volume of units produced.

Based on these estimates, I think it would be possible to build a 200 Watt Solar-In-A-Box system for less than $1,000. That's less than the average flat screen TV. And the cost is heavily dependant on the cost of the solar panels themselves, so mass production and distribution could probably cut that significantly.

If anyone is _seriously_ interested, I'm happy to build a working prototype. If you work for Wal-Mart, I'll even build you a few!

Q: What about rebates?

A: Some existing rebate programs might cover the Solar-in-a-Box system as it is, others might need to be updated. A good strategy for incentives would be to pay the rebates directly to retailers who sell the system to reduce the out-of-pocket cost for consumers. There are already programs that work like this for things like energy efficient appliances and light bulbs. But ultimately, I think the Solar-In-A-Box system would make sense even without any rebates at all, rebates would just make it better.

Q: Why don't you add a charge controller and battery so you can supply power after the sun goes down and harvest the most energy possible?

While this would certainly be possible, I think it is counter-productive.

Batteries are expensive, heavy, and have limited lifetimes. They give back significantly less power than you put into them.

But, more importantly, the best thing about solar power is that you get power when there is the most demand for power, during peak hours on sunny days.

Using a battery would essentially be shifting power generated during peak times to off-peak times, and losing some of the power in the process because batteries are not very efficient.

I think the best use for a Solar-In-A-Box system is to trim peak demand on the grid. This can have a surprisingly high environmental impact because as demand on the grid increases, the efficiency of grid power generation and distribution drops very quickly.

The grid is actually a very efficient source of power when demand is low. Lots of cheap and clean power comes from distant hydroelectric sources. Large modern power plants are also pretty efficient power generators.

But when the grid has reached it limit on sunny summer days, power companies are forced to turn to very high cost and high impact power sources to meet the marginal extra demand. These small, quick responding sources are typically much less efficient than the baseline sources.

By trimming peak demand, you can greatly reduce the need to activate these inefficient power sources.

You can make sure all of the solar power generated by your Solar-In-A-Box system is used by sizing the system correctly. As long as there is enough load connected to the Solar-In-A-Box inverter to use its full output, none will be wasted.

Q: Will the unit do MPPT (maximum power point tracking) on the solar module, for 30% more energy capture?

Yes, MPPT is not hard to do in software and there will already be a little computer inside the inverter anyway. Each solar panel will download its power curve function to the inverter when it is connected, so the inverter can keep each panel at its MPP even if you mix and match different panels on the same system.

Q: Sounds like it will not supply power to the grid so you've avoided UL1741 which is a big headache.

All that is need for a Solar-In-A-Box system is a UL listing. This makes it into an appliance that anyone can bring home and plug in and there is nothing the power company or your local town can do to stop you.

Q: Why not connect the inverter directly into the service panel?

Typically you need a permit and a licensed electrician to do work on the service panel. At very least you need to know what you are doing, so it is not a practical (or safe) do-it-yourself project. Anyone who can plug in a flat screen TV can install a Solar-In-A-Box system.

Questions

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