Grid-tied photovoltaic systems – or PV, use solar panels to create electricity. When the sun strikes these panels, they generate direct-current, or DC power. This power then flows to an inverter, which converts the DC power into the alternating current, AC power used in your home.

If you’re running lights, computers, or other electric loads, your solar will power these loads first.

Any extra power your system makes you sell to the grid, generating a credit, which you can use whenever the sun is not out – at night or when it’s raining. At the end of the month, your credit bill will reflect either a positive credit from your solar electric generation or a bill reduced by as much solar electricity as you sold to the grid. Credits can be carried forward for a year.

With grid-tied solar electric, your home uses power just like it does now – no batteries or funny controllers. With a guaranteed environmental AND economic return on investment, solar power is one of the best investments you can make today.

Solar hot water systems work by capturing the thermal energy present in sunlight and turning it into usable energy in your home.

When solar hot water collectors (either flat plate or evacuated tube style) on your roof are warmer than your water tank, a differential temperature controller activates a pump. This pump then circulates a nontoxic antifreeze mix up to the solar collectors on your roof, where the fluid heats up.

This solar-heated fluid is then pumped to a super-insulated storage tank, where it gives off its heat as it passes through a heat exchanger. It is then pumped back to the roof, continuing the cycle as long as the sun is out.

Should there be unexpectedly high solar thermal gain (or should you be away), the system is designed to automatically go into an overheat protection mode called “Steamback.” Once a certain temperature threshold is hit, the solar circulating pump stops circulating fluid and the fluid present in the collectors turns to steam and fills an expansion tank. The copper elements of the solar hot water collectors are not harmed by high heat and will reach high temperatures until the end of the day. After the system has cooled overnight, the differential temperature controller will reset and allow the system to start running normally the following day.

From May to September, all of the hot water a household uses for washing dishes, clothes or taking showers will be provided by the sun, even on cloudy days. In the darker months of winter, the sun will still help out, but a backup unit – such as a boiler or electric element – will run to ensure a steady supply of hot water. Instead of running all summer, a home’s boiler will only fire up as a backup unit to heat the second coil in the upper part of your tank.

Overall a typical system will produce about 80% of a home’s water heating needs.

Our Solar Road Tour takes us a little further up the coast, where we visit The Highlands in Topsham, a unique retirement community with a strong environmental commitment.

In 2007 The Highlands installed what was Maine’s largest solar hot water system at the time, a 540 evacuated tube system expected to pay for itself in 6 years due to its dramatic reduction in fossil fuel use. The Highlands expanded this year with 24 flat plate solar hot water collectors on their Maine Lodge.

For The Highlands, solar hot water is a win-win: the collectors save their business thousands of dollars a year in fuel costs, while helping to preserve the memorable local environment that appeals to their residents. In this video, we talk to Highlands Sales Consultant, Don Wessels, as he tells us a bit about the system, its value to Highlands, and their commitment to sustainability.

In the second half, we check out a sizzling 48 flat plate solar hot water array on top of Bowdoin’s Thorne Dining Hall… you can see system performance for Thorne (as well as many other campus buildings) online!

Miss Solar Road Tour Episodes?

We’ve had a lot of fun touring Maine and New Hampshire on our journey. Prior videos on our blog:

• Episode 4: SMCC’s Alternative Energy Education Program and Scratch Baking Company
• Episode 3: Paul Ledman’s High Performance Apartments at 62 Cumberland Ave, Portland
• Episode 2: Melissa Coleman on Cranberry Ridge, Freeport Library
• Episode 1: Gritty’s and LL Bean sport solar hot water in Freeport, Maine

More Photos from Our Commercial Solar Photo Gallery:

We’re pleased to be able to show, not tell, the story of Suzanne Huard. A recent retiree, Suzanne fulfilled a long-time solar dream with the installation of an evacuated tube solar hot water system and grid-tied photovoltaic array on her home.

ReVision commissioned NowOrNeverMedia, as part of their “Green Screen TV” series, to cover the story of two solar installations in the middle of a blustery month.

Check out the video on YouTube:

We heard back from Suzanne about the project. She’s pleased to report that “things are going great … I can say now that our daily usage of hot water went down 16+% from our Jan/Feb bill to the prior Dec/Jan bill and the residential electricity went down 11+% (they are metered separately).”

Photos From Our Residential Solar Photo Gallery:

For more installations, see our Solar Projects Map

ReVision’s New Hampshire branch manager, Will Kessler, recently captured this piece of stop motion footage which shows you the process of a solar hot water system and solar electric system coming together on a house in Eliot, Maine!

Watch for the photovoltaic (PV) panels coming in along the top – the solar hot water system consists of the tubes below.

This system will save nearly 300,000 lbs of C02 emissions during its first 30-years of service life.