The meteoric rise of renewable energy has consequences for our electricity supply. While coal and gas fired power stations can generate electricity whenever you need it, renewables are intermittent by nature. So we need a backup plan for when the wind stops or the sun goes down.
All over the world, engineers and scientists are racing to solve one key problem; how to safely and efficiently store electricity at a huge scale but at a low cost. The quest is producing some truly remarkable ideas and this episode details three of them.

More than 2,000 years ago, the thriving city of Petra rose up in the bone-dry desert of what is now Jordan. An oasis of culture and abundance, the city was built by wealthy merchants whose camel caravans transported incense and spices from the Arabian Gulf. They carved spectacular temple-tombs into its soaring cliffs, raised a monumental Great Temple at its heart, and devised an ingenious system that channeled water to vineyards, bathhouses, fountains, and pools. But following a catastrophic earthquake and a slump in its desert trade routes, Petra's unique culture faded and was lost to most of the world for nearly a thousand years. Now, in a daring experiment, an archaeologist and sculptors team up to carve an iconic temple-tomb to find out how the ancient people of Petra built their city of stone. Meanwhile, scientists using remote sensors and hydraulic flumes uncover the vast city and its sophisticated water system. The race is on to discover how these nomads created this oasis of culture in one of the harshest climates on Earth.

In these extraordinary times, there is one thing that can offer solace to everyone – the wonder of the natural world. In the most extreme of environments, from the hottest deserts to the freezing poles, from the highest mountains to underwater kingdoms, animals overcome adversity to survive and thrive, offering a message of hope to humanity.
To raise our spirits, David Attenborough, Hans Zimmer and Dave unite for a special Natural History event – Planet Earth: A Celebration. The special one-hour programme brings together eight of the most extraordinary sequences from Planet Earth II and Blue Planet II including racer snakes vs iguana, surfing bottlenose dolphins and rare footage of the Himalayan snow leopard.

The world's deserts are lands of extremes that force animals to come up with ingenious ways of coping with hostile conditions, giving rise to the most incredible survival stories on earth. A pride of desert lions are so hungry they risk hunting a giraffe several times their size, while male sandgrouse fly 120 miles each day to the nearest waterhole and dice with death to collect water for their chicks. Filmed for the first time, a tiny bat does battle with one of the world's deadliest scorpions, and in Madagascar, a locust swarm of biblical proportions is seen as never before.

Grasslands cover one quarter of all land and support the vast gatherings of wildlife, but to survive here animals must endure the most hostile seasonal changes on the planet. From Asia's bizarre-looking Saiga antelope to the giant anteaters of Brazil, grassland animals have adapted in extraordinary ways to cope with these extremes. In the flooded Okavango, lions take on formidable buffalo in epic battles, on the savannah bee-eaters take advantage of elephants to help catch insects and, on the freezing northern tundra, caribou embark on great migrations shadowed by hungry Arctic wolves.

Experience the world from the viewpoint of animals themselves. From spellbinding wildlife spectacle to intimate encounters, Planet Earth II takes you closer than ever before.
Remote islands offer sanctuary for some of the planet's strangest and rarest creatures. The rare pygmy three-toed sloth enjoys a peaceful existence on an idyllic Caribbean island, while nesting albatross thrive in predator-free isolation. But island life always comes at a cost. On the Galapagos Islands, young marine iguana must escape an onslaught of deadly racer snakes the moment they hatch from the sand. On the sub-Antarctic island of Zavodovski, life gets more extreme still. Every day, one and a half million penguins risk being battered against the rocks by fierce waves as they try to get on and off the island.