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Students from Florida and Cocodrilo engage in environmental projects during an Ocean Doctor-led exchange.

Columbus' ships were leaking, their provisions spoiling. It was clear that they would have to turn back. Yet, anchored off Cuba's southwestern coast near a large, mountainous pine-covered island during his second voyage, Columbus had seen enough. He was convinced Cuba was part of Asia and that return to Spain by land would be possible from the main Cuban island. He ordered each member of the crew sign an affidavit testifying to this, and their signature bound them to have their tongue cut out should they ever contradict their signed statement.

The next day, June 13, 1494, they landed on the nearby island. Columbus named it Evangelista. Over the centuries since, it bore the names Isla de Cotorras (Isle of Parrots), Isla de Tesoros (Treasure Island), Isla de Pinos (Isle of Pines), and finally, Isla de la Juventud (Isle of Youth). While Cuba claimed its sovereignty from Spain in 1898, the fate of the Isle of Pines would not be settled until more than 25 years when it officially became part of Cuba, though by then most of it was controlled by U.S. interests.

Waves break along Isle of Youth's southern coast.David Guggenheim

The 80,000 residents of the island often feel invisible, forgotten and disconnected from the rest of Cuba, an "island within an island." Dwarfed by the massive main island of Cuba, the world is barely aware of its very existence, despite the fact that it is the seventh largest island in the Caribbean, larger than St. Lucia, Barbados, Grenada, Bonaire, St. Croix, St. Thomas, St. John, Aruba, St. Barts, Saba, Terre-de-Haut, Isla Mujeres and Key West combined. The island has struggled for decades, with limited economic opportunities for its residents, mostly in agriculture and fishing. It has long since been forgotten as an international tourist destination.

Location of the community of Cocodrilo on the southern tip of Cuba's Isle of Youth.

The Cuban government has repeatedly tried to infuse life into the island. In 1978, Fidel Castro changed the name to Isle of Youth as part of an effort to bring new opportunity and meaning to the island. An initiative was launched to build a world-class international network of schools on the island, attracting students from Africa, Asia and beyond. Thirty years later, in 2008, Hurricane Gustav, with sustained winds of 155 mph, decimated the island, laying to waste the international schools and that chapter of the island's struggle.

In 2015, Ocean Doctor led an expedition of Cuban and American scientists to visit the protected waters of the Isle of Youth; most of the southern half of the island is protected, part of Cuba's massive system of protected areas. Over our 16 years of working in Cuba, we have found the country as a beacon of hope, where many coral reef ecosystems thrive in sharp contrast to the dead and dying corals elsewhere in the Caribbean.

It is estimated that 50 percent of the coral cover in the Caribbean has vanished since 1970. As we dove among the coral reefs in the Punta Frances protected area, we indeed found some of Cuba's treasured coral reefs, gleaming and healthy. But we also found reefs in stress—some bleached white, some covered in slimy green algae, the telltale signs of a reef beginning to die.

Our Cuban colleagues were surprised. This was something new that they hadn't seen just two to three years earlier. We saw no sharks, no groupers and virtually no large, predatory fish, a sure sign of overfishing which contributes to a reef's decline. Although on paper the area is protected—it has the same level of protection as Cuba's better-known Gardens of the Queen—there is virtually no enforcement and the area is fished illegally.

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Our captain watched with some consternation as an unidentified vessel, gray with no markings, headed straight toward our vessel, anchored more than 50 miles off Cuba's southern coast. Others in the crew speculated nervously about the approaching boat, never previously seen in these parts. The boat pulled alongside and two imposing figures boarded, both in olive military uniforms. A mustachioed representative of the Ministry of Interior stood beside his taller colleague whose uniform, like the boat that carried him, bore no markings at all. A sidearm hung imposingly from his belt. He turned to the captain and requested to meet with Robert F. Kennedy, Jr.

Robert F. Kennedy, Jr. makes a journal entry aboard ship during The Explorers Club's expedition to document unexplored waters off southern Cuba in 2014.David E. Guggenheim

At that moment, Kennedy—a leading environmental activist, president of Waterkeeper Alliance and son of the late Senator Robert F. Kennedy—was 90 feet below the surface with the rest of our group, observing a dozen or so Caribbean reef sharks tracing mesmerizing circles about us. We were carrying the flag of The Explorers Club, visiting and documenting previously unexplored coral reef ecosystems in Cuba's southern waters.

After returning to the boat, the mission of our mysterious guests was revealed. We had been visited by a representative of former Cuban president Fidel Castro's personal guard who had a letter from the Comandante for Kennedy. Mission complete, they posed for a quick photo and departed on the 50-mile journey back to shore and the six-hour drive back to Havana. They had traveled an incredible distance to find us and hand-deliver a letter. We were obviously quite curious as to its contents.

Our captain, Arjel, and the two soldiers that delivered the letter from El Comandante to our vessel.David E. Guggenheim

A few days earlier, Kennedy, Jr. and his family had visited with Castro, who welcomed them warmly. Nearly 52 years prior, Robert Kennedy, serving as U.S. Attorney General, and his brother, President John F. Kennedy, were within a whisker of war with Cuba and the Soviet Union during the Cuban Missile Crisis. The quiet Castro-Kennedy, Jr. meeting was historical. Relations between Cuba and the U.S. were warming, though the dramatic announcement of normalization of diplomatic relations would not occur for another six months.

Kennedy, Jr. shared the letter with me, a polite set of Castro's reflections on the meeting and kind words for Kennedy and his family. What I found especially significant in the letter was his discussion about oceans:

"For many years I was a passionate spearfisherman without the proper awareness of the beauty and value of coral reefs. Through this I knew some of the experiences of Jacques-Yves Cousteau, who in such a way fell in love with the sea that ended up becoming one of the most famous defenders of the life and the value of the seas. Today it is known that the sea is one of the largest and varied sources of protein foods. These factors helped me understand the importance of the services you have rendered to the people of the United States and other nations of the world in their struggle to protect the environment."

The influence of Cousteau on Castro has been a recurring theme I have heard from Cuban colleagues during my many years working in Cuba. Castro read and was influenced by Cousteau's books and, in 1985 when Cousteau visited the island to make a documentary, the two finally met and shared a special friendship. Castro granted Cousteau with rare privilege during his visits. Cousteau and his team became the first non-Cubans to pass through the gate of the U.S. Navy's Guantanamo Bay installation since 1962. He is reported to have freed dozens of political prisoners at Cousteau's request. And Castro spent a great deal of time with Cousteau, dining with him aboard his vessel, Calypso.

Jacques-Yves Cousteau's Vessel, Calypso, in Havana Bay (1985)Cousteau Society

In the late nineties, aboard another research vessel visiting from the U.S., Castro reflected on his friendship with Cousteau and said, "You know, he loved exploring Cuban waters because of our protection." In the Cousteau documentary, Cuba: Waters of Destiny, Cousteau is clearly taken with what he observes in Cuba: "My first dive in the waters of Cuba serves as a moment of truth…around me, large fish among flourishing coral, a reef more rich than any I have seen in years," a stunning reminder that even 30 years ago, the unraveling of coral reef ecosystems in the Caribbean was well underway. Today it is estimated that the Caribbean has lost half of its coral cover. Spared in part by a history that has caused Cuba to develop profoundly differently than the rest of the Caribbean, coupled with world-class environmental laws, many of Cuba's coral reef ecosystems have been spared the demise observed throughout the Caribbean.

Before allowing the Calypso to depart Cuba's waters, Castro challenged Cousteau, asking him why he didn't have a Cuban scientist aboard. Consequently, Cousteau later welcomed Dr. Gaspar Gonzalez Sansón, former vice director of the University of Havana's Center for Marine Research, to serve as a visiting scientist aboard Calypso in New Zealand. Years later, Dr. Gonzalez would become our co-principal investigator for a decade of expeditions off Cuba's northwestern coast and regaled us with hilarious tales of a Cuban among Frenchmen aboard Calypso.

Captain Jacques-Yves Cousteau (left) and Dr. Gaspar Gonzalez Sansón (right) on the bow of the Calypso in New Zealand. At the request of Fidel Castro, Dr. Gonzalez served as a visiting scientist during Cousteau's "Rediscovery of the World" expedition.

The friendship of Cousteau and Castro continued and strengthened in environmental solidarity at the Rio Earth Summit in 1992 where Castro delivered a sharply-worded and uncharacteristically brief address, imploring the developed world to "stop transferring to the Third World lifestyles and consumer habits that ruin the environment. Make human life more rational." In early 1998, less than six months after Cousteau passed away, Castro fondly remembers a playful encounter with Cousteau at the Rio Earth Summit: "They have all the heads of state lined up for a 'photo op' in Rio, and I pulled him [Cousteau] up with me, and say, 'Captain, join this picture in the 'photo op' because most people here know nothing about the environment. And he came up and was in the 'photo op' with all of us."

President Fidel Castro and Captain Jacques-Yves Cousteau in a playful exchange at the Rio Earth Summit in 1992.

In July 1997, Cuba enacted Law 81, the Law of the Environment, a truly impressive set of laws and regulations meant to reverse the environmental damage from prior decades and chart a path of sustainability. Within a decade, Cuba banned the destructive fishing practice of bottom trawling from its waters. Today, Cuba has nearly met its goal of protecting 25 percent of its marine waters in marine protected areas, one of the largest percentages in the world. (In comparison, the world average is currently 2-3 percent). Many Cubans attribute Law 81 and Cuba's ongoing commitment to the environment to Castro's environmental ethic, which the Comandante, in part, attributes to Cousteau.

With the passing of Castro and a possible retreat on Cuba relations by an incoming Trump Administration, there is a growing uneasiness about Cuba's uncertain future. Facing profound economic need and unprecedented growth pressure, especially in response to plans more than triple tourism by 2030, Cuba will be put to the test in the months and years ahead. For now, Cuba remains a green, unspoiled jewel in the Caribbean. It is a place where policy is still informed by science and fact, and decisions governed by its laws.

By 2014, it had been some time since Castro had last donned a mask and personally explored Cuba's waters, but it was clear that his passion and curiosity for the sea was as strong as ever. In his letter, Castro made a simple but urgent request of Kennedy, Jr: "Today, I beg you, if you have a few minutes, tell me about the general impression of what you have seen on the bottom..." Several weeks later, Kennedy complied and assured the Comandante that for now, Cuba's marine ecosystems were still healthy and spectacular.

MAXSHOT / iStock / Getty Images

Solar panels allow you to harness the sun's clean, renewable energy, potentially cutting your electric bills as well as your environmental footprint. But do solar panels work on cloudy days, or during seasons of less-than-optimal sun exposure? For homeowners who live outside of the Sun Belt, this is a critical question to consider before moving ahead with solar panel installation.

In this article, we'll go over how solar panels work on cloudy days, whether solar panels work at night, and how to ensure you always have accessible power — even when your panels aren't producing solar energy.

How Solar Panels Work on Cloudy Days

Photovoltaic (PV) solar panels can use both direct and indirect sunlight to generate electrical power. This means they can still be productive even when there is cloud coverage. With that said, solar panels are most efficient and productive when they are soaking up direct sunlight on sunny days.

While solar panels still work even when the light is reflected or partially obstructed by clouds, their energy production capacity will be diminished. On average, solar panels will generate 10 to 25% of their normal power output on days with heavy cloud coverage.

With clouds usually comes rain, and here's a fact that might surprise you: Rain actually helps solar panels work more effectively. That's because rain washes away any dirt or dust that has gathered on your panels so that they can more efficiently absorb sunlight.

Do Solar Panels Work at Night?

While solar panels can still function on cloudy days, they cannot work at night. The reason for this is simple: Solar panels work because of a scientific principle called the photovoltaic effect, wherein solar cells are activated by sunlight, generating electrical current. Without light, the photovoltaic effect cannot be triggered, and no electric power can be generated.

One way to tell if your panels are still producing energy is to look at public lights. As a general rule of thumb, if street lamps or other lights are turned off — whether on cloudy days or in the evening — your solar panels will be producing energy. If they're illuminated, it's likely too dark out for your solar panel system to work.

Storing Solar Energy to Use on Cloudy Days and at Night

During hours of peak sunlight, your solar panels may actually generate more power than you need. This surplus power can be used to provide extra electricity on cloudy days or at night.

But how do you store this energy for future use? There are a couple of options to consider:

You can store surplus energy in a solar battery.

When you add a solar battery to your residential solar installation, any excess electricity can be collected and used during hours of suboptimal sun exposure, including nighttime hours and during exceptionally cloudy weather.

Batteries may allow you to run your solar PV system all day long, though there are some drawbacks of battery storage to be aware of:

  • It's one more thing you need to install.
  • It adds to the total cost of your solar system.
  • Batteries will take up a bit of space.
  • You will likely need multiple batteries if you want electricity for more than a handful of hours. For example, Tesla solar installations require two Powerwall batteries if your system is over 13 kilowatts.

You can use a net metering program.

Net metering programs enable you to transmit any excess power your system produces into your municipal electric grid, receiving credits from your utility company. Those credits can be cashed in to offset any electrical costs you incur on overcast days or at night when you cannot power your home with solar energy alone.

Net metering can ultimately be a cost-effective option and can significantly lower your electricity bills, but there are a few drawbacks to consider, including:

  • You may not always break even.
  • In some cases, you may still owe some money to your utility provider.
  • Net metering programs are not offered in all areas and by all utility companies.

Is Residential Solar Right for You?

Now that you know solar panels can work even when the sun isn't directly shining and that there are ways to store your energy for times your panels aren't producing electricity, you may be more interested in installing your own system.

You can get started with a free, no-obligation quote from a top solar company in your area by filling out the 30-second form below.

FAQ: Do Solar Panels Work on Cloudy Days?

How efficient are solar panels on cloudy days?

It depends on the panels, but as a rule of thumb, you can expect your solar panels to work at 10 to 25% efficiency on cloudy days.

How do solar panels work when there is no sun?

If there is literally no sunlight (e.g., at night), then solar panels do not work. This is because the photovoltaic effect, which is the process through which panels convert sunlight into energy, requires there to be some light available to convert.

However, you can potentially use surplus solar power that you've stored in a battery. Also note that solar panels can work with indirect light, meaning they can function even when the sun is obscured by cloud coverage.

Do solar panels work on snowy days?

If there is cloud coverage and diminished sunlight, then solar panels will not work at their maximum efficiency level on snowy days. With that said, the snow itself is usually not a problem, particularly because a dusting of snow is easily whisked away by the wind.

Snow will only impede your solar panels if the snowfall is so extreme that the panels become completely buried, or if the weight of the snow compromises the integrity of your solar panel structures.

Will my solar panels generate electricity during cloudy, rainy or snowy days?

Cloudy days may limit your solar panel's efficiency, but you'll still be able to generate some electricity. Rainy days can actually help clean your panels, making them even more effective. And snowy days are only a problem if the snow is so extreme that the panels are totally submerged, without any part of them exposed to the sun.

David Guggenheim
Insights Writers
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