Solar 101: How Does Solar Energy Work?

Our sun is a naturally occurring nuclear reactor. It releases tiny packets of energy called photons, which travel the 93 million miles from the sun to Earth in about eight-and-a-half minutes. Every hour, enough photons impact our planet to theoretically satisfy global energy needs for an entire year. However, solar-generated power currently accounts for just four-tenths of one percent of the total energy consumed in the United States. Solar technology is improving and costs are dropping rapidly, though, so our ability to harness the sun’s abundance of energy is on the rise. In fact, a report from the International Energy Agency indicates that solar energy could become the largest global source of electricity by 2050. In the coming years, we will all be enjoying the benefits of solar-generated electricity in one way or another.

So how does solar power work?

Photovoltaic solar panels

Photovoltaic (PV) solar panels are made up of many solar cells. Solar cells are made of silicon, like semiconductors. They are constructed with a positive layer and a negative layer, which together create an electric field, just like in a battery. When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels (modules) can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.

Basics of electricity

PV solar panels generate DC (direct current) electricity. With DC electricity, electrons flow in one direction around a circuit. This example shows a battery powering a light bulb. The electrons move from the negative side of the battery, through the lamp, and return to the positive side of the battery.

With AC (alternating current) electricity, electrons are pushed and pulled, periodically reversing direction, much like the cylinder of a car’s engine. Generators create AC electricity when a coil of wire is spun next to a magnet. Many different energy sources can “turn the handle” of this generator, such as gas or diesel fuel, hydroelectricity, nuclear, coal, wind, or solar.

AC electricity was chosen for the U.S. electrical power grid, primarily because it is less expensive to transmit over long distances. However, solar panels create DC electricity. How do we get DC electricity into the AC grid? We use an inverter.

Inverters

A solar inverter takes the DC electricity from the solar array and uses that to create AC electricity. Inverters are like the brains of the system. Along with inverting DC to AC power, they also provide ground fault protection and system stats including voltage and current on AC and DC circuits, energy production, and maximum power point tracking.

Central inverters have dominated the solar industry since the beginning. The introduction of micro-inverters is one of the biggest technology shifts in the PV industry. Micro-inverters optimize for each individual solar panel, not for an entire solar system, as central inverts do. This enables every solar panel to perform at maximum potential. One solar panel won't drag down the performance of entire solar array, as opposed to central inverters that optimize for the weakest link.

Putting it all together

Here’s an example of how a residential solar energy installation works. First, sunlight hits a solar panel on the roof. The panels convert the energy to DC current, which flows to an inverter. The inverter converts the electricity from DC to AC, which you can then use to power your home. It’s beautifully simple and clean, and it’s getting more efficient and affordable all the time.

However, what happens if you’re not home to use the electricity your solar panels are generating every sunny day? And what happens at night when your solar system is not generating power in real time? At this point, we don’t store solar-generated energy for later use, so it flows back into the grid. But don’t worry, you still benefit through a system called “net metering.”

Net metering

A grid-tied PV system has no batteries. So when the sun is shining and the solar user doesn’t use up all the energy generated in a day, excess power is sent out of the house to neighbors’ houses. This is called “back feeding” the grid. At night, the grid will provide energy for lights and other appliances as usual, so solar users are covered in exchange for the excess energy they shared with the grid during the day. A net meter records the energy sent compared to the energy received from the grid.

There are now over 20,000 megawatts of cumulative solar electric capacity operating in the United States. Around 650,000 homes and businesses have now gone solar. In 2014, a new solar project was installed every two-and-a-half minutes. The growth of solar capacity is projected to double in the next two years. Solar energy is truly the wave of the future, and we at SunPower believe the sun belongs to everyone. We’re committed to unlocking its vast energy so all of us can enjoy the freedom it provides. It all starts with a single solar cell.

*Source: SunPower Corporation [US]

WHAT CAUSES ICE DAMS AND ICICLES?

Anyone who has lived in a snowy climate has seen ice dams. Thick bands of ice form along the eaves of houses, causing millions of dollars of structural damage every year. Water-stained ceilings, dislodged roof shingles, sagging gutters, peeling paint, and damaged plaster—all are the familiar results of ice dams.

There are many ways to treat the symptoms, but proper air sealing, insulation, and attic venting are the best way to eliminate the problem.

Ice dams form along the roof's edge, usually above the overhang. Here's why. Heat and warm air leaking from the living space below melt the snow, which trickles down to the colder edge of the roof (above the eaves) and refreezes. Every inch of snow that accumulates on the roof insulates the roof deck a little more. This keeps more heat in the attic, which in turn makes the roof even warmer and melts more snow. Frigid outdoor temperatures ensure a fast and deep freeze at the eaves. The worst ice dams usually occur when a deep snow is followed by very cold weather.

The Havoc Ice Dams Wreak

Contrary to popular belief, gutters do not cause ice dams. However, gutters do help to concentrate ice and water in the very vulnerable area at the edge of the roof. As gutters fill with ice, they often bend and rip away from the house, bringing fascia, fasteners, and downspouts in tow.

Roofs leak on attic insulation. In the short term, wet insulation doesn't work well. Over the long term, water-soaked insulation remains compressed, so that even after it dries, the R-value is not as high. The lower the R-values, the more heat lost. This sets up a vicious cycle: heat loss-ice dams-roof leaks-insulation damage-more heat loss! Cellulose insulation is particularly vulnerable to the hazards of wetting.

Water often leaks down inside the wall, where it wets wall insulation and causes it to sag, leaving uninsulated voids at the top of the wall. Again, energy dollars disappear, but more importantly, moisture gets trapped in the wall cavity between the exterior plywood sheathing and the interior vapor barrier. Soon you can smell the result. In time, the structural framing members may decay. Metal fasteners may corrode. Mold and mildew may form on the surface of the wall. Exterior and interior paint blisters and peels. As a result, people with allergies suffer.

Peeling paint deserves special attention here because it may be hard to recognize what's causing it. Wall paint doesn't usually blister or peel while the ice dams are visible. Paint peels long after the ice—and the roof leak itself—have disappeared. Water from the leak infiltrates wall cavities. It dampens building materials and raises the relative humidity inside the wall. The moisture within the wall cavity tries to escape (as either liquid or vapor) and wets the interior and exterior walls. As a result, the walls shed their skin of paint.

Solving the Problem

The way to stop ice dams from forming is to keep the entire roof cold. In most homes this means blocking all air leaks leading to the attic from the living space below, increasing the thickness of insulation on the attic floor, and installing a continuous soffit and ridge vent system. Be sure that the air and insulation barrier you create is continuous.

Don't waste time or money placing electric heat tape on the shingles above the edge of the roof. Electrically heated cable rarely, if ever, solves the problem. It takes a lot of electricity to prevent ice formation; and the heating must be done before it gets cold enough for ice dams to form, not afterwards. Over time, heat tape makes shingles brittle. It's expensive to install, too, and water can leak through the cable fasteners. And often the cables create ice dams just above them.

The worst of all solutions is shoveling snow and chipping ice from the edge of the roof. People attack mounds of snow and roof ice with hammers, shovels, ice picks, homemade snow rakes, crowbars, and chain saws! The theory is obvious. No snow or ice, no leaking water. Unfortunately, this method threatens life, limb, and roof.

*Source: Home Energy Saver

Interested in Solar? If you live in WA, schedule an comprehensive in-home energy audit today!

Are you a Washington State Resident Interested in Solar Energy? 

1) Respond to this post if you would like to schedule a complimentary in-home energy evaluation.

2) We don't just do solar! We also offer Ductless Heating & Cooling, Insulation, and many other services to help you live more comfortably in your home! 

How Much Does it Cost to Install Solar on an Average US House?

In the USA, a rule of thumb is that the average house consumes electricity at the rate of 1 kW per hour (kWh). There are about 730 hours in each month, and the average price of a kWh of electricity is $0.10. So an average monthly bill would be around $73 for 730 kWh of electricity.

Of course, this can vary considerably if you have non-standard items such as a hot-tub, or some electrical appliances running continuously. Extended computer use, plasma screen TVs and video games consoles can also make an impact. Your usage will increase significantly in months when you run an air conditioning unit, as well. Finally, the cost of electricity varies widely across the USA, from as low as $0.07/kWh in West Virginia to as much as $0.24/kWh in Hawaii. You’ll have to adjust my guidelines accordingly, because they apply to an average home with average consumption and average electricity costs.

A conservative value to use as a solar panel’s generating capacity is 10 watts/sq. ft. This represents a panel conversion efficiency of about 12%, which is typical. This means that for every kW you generate, you need about 100 sq. ft. of solar panels. If the sun shone 24 hours a day, you could put up 100 sq. ft. of panels and have enough energy to power the average home.

But, as we all know, the sun is available only during daylight hours, and the amount available per day is highly dependent on the extent of cloud cover. Also, the length of each day is dependent on the season. Fortunately, there are resources on the web to help you figure out how many hours per day (on average) you can count on the sun to shine, based on where you live.

The averages across the USA vary from around 3 hours per day in places like Seattle, Chicago, and Pittsburgh, to 5 or 6 hours per day in states like Colorado and California, to a high of 7 hours per day in Arizona. What that means is that the size of the panel array required can vary, anywhere from 400 sq. ft. to 800 sq. ft. (i.e., 4 kW to 8 kW), depending on where you live. You’ll need more panels if you live in a location that gets less sunshine per day, and fewer if you live in a location that gets more.

If your utility company allows you to have net metering — that is, they supply you with a special meter that will spin backwards when you generate more electricity than you use — your annual bill can average out at zero. Because of shorter days in the winter, you’ll likely be a net purchaser of electricity in that season and a net producer in the summer months. A grid-tied system like this is different than off-grid systems used in remote locations with no electrical service; those require batteries, which can significantly increase overall system costs.

At the time of this writing, the installed cost of solar panels was between $7-$9 per watt: A 5 kW system would cost around $25,000-$35,000. Many utility companies offer incentives, and some subsidize as much as 50% of system costs. Even at half the cost, though, a system that generates an average $75 of electricity per month could take a long time to pay for itself.

For example: A system that costs $18,000 has a payback period of about 20 years. The cost of a solar panel today is around $3 per watt, and the extra cost of installation brings costs up to $5- $6 per watt. Note: Installation costs for PV systems include both labor and the electronics needed to tie the solar array into your existing electrical system.

Standard Solar System Components

This brings up an important point: it takes more than a solar panel to get a PV system up and running, though. In fact, there are generally four components in every PV system:

1. Solar panels – captures sun’s energy and converts it to electricity
2. Controller – protects batteries by regulating the flow of electricity
3. Batteries – store electricity for later use
4. Inverter – converts energy stored in a battery to voltage needed to run standard electrical equipment

The entire system is what drives the cost of solar up and equipment like batteries need to be replaced over time.

The good news is that the costs for solar panels are expected to continue to drop, as thin film panels from companies like First Solar, Nanosolar, and AVA Solar become available to the residential market. Right now, though, First Solar is only selling to commercial customers. Nanosolar and AVA Solar have yet to ramp up their production facilities. It will be interesting to see where this all goes in the next year or two, since these companies are talking about very aggressive price targets — in the order of $1-2 per watt — and volumes that are several times today’s total output.

Assuming that installation and auxiliary equipment costs can be reduced to around $1 per watt, then a 5 kW system may cost as little as $10,000, and the payback period would be 10 years, even without subsidies. This makes PV solar installations much more attractive. Of course, all this assumes that electric rates stay constant.

However, they are likely to rise as fuel and other infrastructure costs increase, so payback periods may be even shorter in the future. In the meantime, expect to see more PV solar panels installed on roofs, especially in areas with favorable solar conditions or with higher-than-average electricity rates.

*Source - All credit goes to the original creator.