The San Diego County Water Authority has an unusual plan to use the city’s scenic San Vicente Reservoir (水库) to store solar power so it’s available after sunset. The project could help unlock America’s clean energy future.

Perhaps ten years from now, if all goes smoothly, large underground pipes will connect this lake to a new reservoir, a much smaller one, built in a nearby valley about 1100 feet higher. When the sun is high in the sky, California’s abundant solar power will pump water into that upper reservoir. It’s a way to store the electricity. When the sun goes down and solar power disappears, operators would open a valve (阀门) and the force of 8 million tons of water, falling back downhill through those same pipes, would drive machines capable of producing 500 megawatt s of electricity for up to eight hours. That’s enough to power 130, 000 typical homes.

“It’s a water battery!” says Neena Kuzmich, Deputy Director of Engineering for the water authority. She says energy storage facilities like these will be increasingly critical as California starts to rely more on energy from wind and solar, which produce electricity on their own schedules, without considering the demands of consumers. Californians learned this during a heat wave this past summer. “Everybody in the state of California got a text message at 5:30 in the evening to turn off their appliances,” Kuzmich says. The sun was going down, solar generation was disappearing, and the remaining power plants, many of them burning gas, couldn't keep up with demand. The reminder worked: people stopped using so much power, and the grid (电网) survived.

Yet earlier on that same day, there was so much solar power available that the grid couldn’t take it all. Grid operators turned away more than 2000 megawatt hours of electricity that solar generators could have delivered, enough to power a small city. That electricity was wasted. There was no way to store it for later, when operators desperately needed it.

When plumbing (水暖设备) makes funny noises, it’s not always a good sign. But John Kovac, a harpist (竖琴演奏者) from Virginia, likes the pipes to sing. He thinks plumbing pipes make good musical instruments.

Kovac has made standard harps out of wood for more than 20 years. He says he feels excited when he creates an instrument with his hands and uses it to make music come alive. But it takes years of training and special tools to make a traditional musical instrument. Kovac wanted to share the joy of making instruments with people who might not have the time or money to do it. So he decided to find an easier way.

Plumbing was the answer. Kovac found PVC pipes at a local store. PVC pipes are the white tubing that many plumbers use. You might find some in your house under a sink or in the basement. Kovac says that PVC pipes are great for making instruments because they are inexpensive, come in many shapes and sizes, and fit together perfectly.

Kovac makes harps, guitars, violins, and drums out of PVC pipes. He also makes uncommon instruments like the udu from Nigeria. His instruments may look as if they come from outer space, but they really work. He and some of his music students and friends even started a band called the East Coast PVC Band.

Sally Seabright is a violin teacher who plays the PVC violin with the band. At first, the rounded shape of the PVC violin made it difficult to hold between her chin and shoulder, but Kovac made a slight change by adding a piece that fits perfectly under her chin. That kind of adaptability is what Kovac admires about PVC. He says, “I know it’s not easy for the average person to make a musical instrument, but I hope to enable anyone who has ever dreamed of making a violin, harp, or guitar to fulfill his or her dreams.”

Astronauts on the International Space Station will soon test a new oven for making chocolate chip cookies. A spaceship carrying the cooking equipment and other supplies was launched on Saturday from the Wallops Flight Facility in the United States. The shipment, weighing 3,700 kilograms, reached the space station on Monday.The goal is to explore the possibility of making freshly baked cookies for space travelers.

American company Nanoracks designed and built the oven and helped with organizing the flight to the space station.Hilton DoubleTree hotels supplied the cookie dough(生面团）the astronauts will use.

In the past,space station crews have created their own pizzas using a thin,flat piece of bread known as flatbread.Astronauts have tried other creative ways to make food, such as creating salads from vegetables grown in the space station.Results have been mixed.

The cookie baking will be a slow process.The oven can heat just one cookie at a time.The test could take weeks before the astronauts have chance to try out freshly baked cookies.

Five unbaked cookies have been in a space station freezer for several weeks.Each is in its own individual clear bag made out of silicone.The oven can heat foods to temperatures as high as 177 degrees Celsius.That is twice the temperature of the U.S.and Russian food warmers on the space station.The oven uses electric heating elements.

Mary Murphy is with Nanoracks.Murphy says she expects a baking time of 15 to 20 minutes for each cookie when the oven is heated to about 163 degrees Celsius.She adds that the smell of baking cookies should fill the space station each time a cookie comes out of the oven.

The oven's first use will be the real test.Without the force of gravity, the astronauts do not know exactly how the cookie will look.Three of the space-baked cookies are to be returned to Earth for testing.