this is bbc news. the headlines — women in saudi arabia are celebrating as the country finally lifts its controversial driving ban. the new ruling came into force at midnight local time by royal decree. but saudi women are still not free to travel, marry, divorce or even leave prison without the permission of a male relative. zimbabwe is in shock after its president, emmerson mnangagwa, escaped unhurt from an explosion, which he's described as an assassination attempt. mr mnangagwa hinted that political opponents within the ruling party might be responsible for the attack. new zealand's prime ministerjacinda ardern and her partner, clark gayford, have introduced their new daughter to reporters outside the hospital in auckland where she was born. the little girl, who's just 3 days old, has been named neeve. now on bbc news, it's time for click. this week: robot hunts killer

starfish, hurricane in a tube, and gravity train runs out of steam. florida, america's sunshine state — and home to the us's first sustainable town. this is babcock ranch. powered, befittingly, almost entirely by that big burning

ball in the sky. it's 33 degrees. that humidity, i believe, about i,000,000%. and i've come to a solar field, so you don't have too 343,000 solar panel spent some 440 acres, providing 75 megawatts of electricity. that's enough to power 15,000 homes. one of the big problems with solar energy has been when the clouds, over or especially when it gets dark, the whole thing effectively goes dead. and we haven't really had a way of storing solar energy until very recently. but over there, ten buildings full of batteries. so it's a start. a pretty good one, too. babcock has the largest combined solar and storage facility in the us. the batteries can store 40 megawatt hour of electricity, which is enough to keep around 2000 average us homes alight forfour hours. of course, lithium batteries

are just one way of storing energy to use later. we've seen other methods before. there's electric mountain in wales, which holds water at a top reservoir until power is needed, it then releases it back down to the lake below. switzerland's air cave fills itself with compressed air and then blows it out to turn turbines. now, over in california, kate russell is on track to see a new solution. since the oil crisis of the 1970s, california has invested heavily into wind and solar power, with the latest state legislation calling for 50% renewable energy by 2030 and all new homes must have solar within two years. the state is way ahead of its target, so much so that they've had to start paying neighbouring states to take some of the energy from them. as we've heard before, the problem is storage.

the grid was built to handle fossil fuel generated power and storage solutions like hydroelectric dams are in short supply. batteries, too, are very bad for the environment, turning unused renewable energy into not such a green solution. california—based company aries have come up with one alternative. aries was really an attempt to think of a way to use the inexhaustible, always reliable power of gravity. we know gravity is going to be there for us. we don't have to worry about shortages or any of that. so how do we use gravity to store and then discharge power when we need it? one of the most efficient ways to move mass, which people have spent billions of dollars to perfect, are railroads. right. 150 years of experience, incredibly efficient, steel wheels on steel rails are one of the most efficient ways to move mass. dubbed the gravity train,

energy is used in electricity to push its weight uphill. when you want to take the energy out you let gravity pull the train back down, using the friction braking to slow the train in order to make power. it's the same way hybrid electric cars like the prius work. you see those wind turbines behind me, they're completely still, even though there is clearly plenty of wind right now. it's not because they're broken, it's because there is no more room to store the energy they would create. and that's the problem the gravity train well solve. when you are into access energy production, use it to power the train up a hill, when you want the energy back, centre the train back down again. this demo train carries almost five tonnes uphill, storing energy as it goes. a full—scale installation will return 80% of the stored energy, which is not quite as efficient as a huge dam, but has a lot less impact. the amount of energy we store is the weight of the train times the height of the hill.

simple mathematics. so the more weight and the higher the hill the more energy we can store. we need long, gently sloping plains. we had clients who approached us and said i only have steep, rocky, craggy mountains, so we have developed a new variation on the aries technology at almost vertical. in october, the company breaks ground on the first full—scale aries in the state of nevada. it'll be used to fine tune the inconsistent energy flows that are a natural part of using solar and wind power. minute by minute it will trim the imbalance between load and generation on the grid, so our trains may need to go uphill for a minute, they need to go downhill forfive minutes, they are constantly acting like a large flywheel that allows the grid to stay at exactly 60 hertz. it's early days yet and the concept

has still to be proved in nevada, but it could help solve one of the renewable industries biggest conundrums right now, balancing the ebb and flow of nature made enemy in a more substantial way. after we run 30 or 40 years providing energy storage and helping people we can remove all of our facilities very quickly, 96% of them can be either repurposed or recycled, so only 4% of our facilities could ever go into a landfill. we are trying to reduce that. we can then plant some native vegetation and six months later you would never know our facility was there. that was kate on a roll in california. back at babcock i'm going for a solar powered speed in an autonomous shuttle, with its chief financial officer. i guess the motivation for having these autonomous vehicles is that you're encouraging families

here to not have as many cars. correct. 0ur thought is that over time most families in the us have a two car family. our hope is that we can get from a two car to a one carfamily. where you have a car for the family, perhaps, but if you have it for a commuterfor work you won't need it any more, you can take an autonomous shuttle or an autonomous vehicle to work. over time, which will take a long time, perhaps, there are no cars. i think, realistically, within the next 10—15 years you can see a time when you go from two car to one car. you think the us government at the moment doesn't... i think they get it. i think they're getting it. the government's a little slow to move, typically. in major cities, major metros, where traffic and pollution are an issue, technology can come in and save a lot of that. i think governments are willing to step up and make sure this comes to fruition. we're seeing that slowly. what we're hearing and reading about it a lot of major urban cores are going to become, there will be restricted access, if you're driving your car

and you're trying to get there you can't get there — up to a certain mile, three miles outside of the city core you you can't get in to the city core without being in an autonomous vehicle, for instance. but outside of autonomous vehicles, building a city or a town that is sustainable, you're not going to be able to do this in colder, more crowded parts of the world. i think that's right. we have a unique situation here, we have the benefit of scale. there are not many people who have 1000 acres of land. that is a big chunk of dirt. along with autonomous shuttles, babcock has its own water and waste facilities, and as and as well as reclaiming water, there is a restriction on the amount you are allowed to use. the tin roofs reflect heat, making homes 10% better at keeping cool, and the ranch's on—site gym is environmentally friendly, too, it's powered by the treadmills. 0ne incentive to get off the couch, i suppose. it is a commendable vision to build a town with all these sustainable values, but i can't help thinking

can only really do this when you are building a community from scratch. i mean, could you imagine trying to retrofit an existing town with all of these technologies? you basically have to tear up the infrastructure and tear down all the buildings and start from scratch anyway. babcock has been built in the style of older towns, to attract those who aren't necessarily fans of a new build feel. hi. are you expecting me? people like the kinleys. do you mind if ijust step inside your air—conditioning and stay here forever? they've got a robot vacuum cleaner, a coffee making fridge.... it's set up so it won't spill all over the place. ..and an electric car. for richard, a self—confessed geek and a real fan of click, babcock was his calling. just reading tech blogs all the time on the internet and it sounded

fascinating to me. i liked the idea that it was environmentally friendly and was looking forward as far as energy solutions. in atlanta, we lived just downwind from one of the biggest coal polluting plants in the country. i thought that cannot be healthy. i think of it as guilt—free living. in the uk when you have a small town with a central area and you can walk to, it encourages walking, so it's the lifestyle. and while the buildings may look like historic florida, for me it was also all the technology, you know, having 1 gigabyte of fibre optic, internet in the homes... yeah, you definitely like that. hello and welcome to the week in tech. it was the week that the world health organization classified gaming disorder as a condition capable of causing debilitating addiction. arguing with your malfunctioning

tech could soon become a whole lot more intellectually stimulating. ibm put it's project debtor to the test this week. the system listens to the arguments of its human opponent and then scans hundreds of millions of documents in its memory to construct what it considers to be a sound and logical argument. having analysed the data, i will argue... ever wished you'd caught something in slow motion after you filmed it? well, chip designer nvidia shows us how ai could be used to fill in the gaps, turning 30 frames per second footage into 240 frames per second slick slow motion. and finally, the battle for our eyes and ears is hotting up. facebook has gone head to head with youtube, with plans to let social media stars into its previously high end watch programme. meanwhile, facebook owned instagram

revealed plans to host longer videos on the platform, much like youtube. and youtube itself has been busy launching its subscription service, making content available off—line in 12 more countries, including the uk. confused? just go watch a video and relax. hurricane season is just around the corner in the us and that means that south florida is once again at risk from deadly winds and storm surges. much of it lies less than five metres above sea level. miami airport is just one metre. and in the further future, even moderate estimates of climate change will mean that the sea will swallow much of this area by the year 2100.

it's probably no surprise that some of the most advanced hurricane research in the world is going on here at the university of miami. this is a hurricane simulator. it is a 23—metre long glass tank filled with water and connected to an enormous fan, which means they can generate the strongest winds over water anywhere in the world. up there they can simulate a category 5 hurricane. a 1500 horsepower motor drives 65 metre per second winds, whipping up spray and smashing waves into whatever they put in the tank. the sensors in the tank measure how those waves behave and what they do to florida's buildings. because it's not so much the winds as the storm surge. the water driven inland by the storm that causes so much destruction and loss of life.

in a hurricane, two metres of floodwater is accompanied with large waves on top of that and the wave leading is really dramatic. it is what we are talking about, with waves that are quite often breaking and coming and hitting the structure. it's an impulsive force but it is repeated, many times, during a storm. even if it's only an hour, that can really do dramatic damage. and what have you found so far? how can you build houses better now because of what you have found? one of the key things we have found in some recent measurements related to the structures directly, is that often, with decking, it is actually where the wave gets trapped underneath it. that is like an explosive uplift force. so you really have to look at how you engineer the attachments on things. 0k, we are about to go to full speed.

ok, here comes the spray now. understanding the forces on these models will help develop new guidelines on what support structures would help a building withstand the onslaught of a storm surge. so if somehow you were under the sea during a hurricane, this is where you would see. it's better than being on top, i can tell you that. have you ever been in there when it's on category five, even in your christmas parties? no, we wouldn't go in there, because there's not much to hold on to and in the back of it it's like cheese slicer. so i don't really want to be turned into sausage or cheese.

the team here aren'tjust trying to make stronger buildings. they are also testing ways of stopping the full force of the waves from getting to the land in the first place. here, they are looking at the effect of the seawall on protecting the house. further out in the water, something you might not expect. a coral reef. we've actually been reading some global studies which show that wave energies actually dissipated 97%, on average, as waves hit a reef crest and go towards shore. so they act like 97% efficient wave break? that's right, if it's a healthy reef with a reef crest. it doesn't look to me like there's that much coral there. and it doesn't come to the surface. does that really do a good job? it can, actually, yes. with the waves you have the kind of circular motion that happens at the top, it causes circular motion all the way down, in a little ellipsis

down to the sea floor. anything that disrupts that helps to slow down the wave. the problem is thatjust when we need coral to protect from climate change, climate change is killing coral. although corals, much like the trees in the rainforest, are the habitat builders of the ecosystem, it you lose the corals, just like if you lose the trees in the rainforest, you end up with no ecosystem. the corals building that habitat are very thermally sensitive. they are some of the most climate change sensitive species on the planet. the reason they are so sensitive to climate change is because they are very vulnerable to small changes in temperature. an unusually hot summer causes a coral to turn white,

in a process we call coral bleaching. that's a process whereby this symbiosis between the coral animal and this tiny single cell plants that live inside its tissue, that symbiosis breaks down and the coral spits out its algae, turns white, and unless it can somehow recover those algaes it will die. it starves, from lack of food. andrew baker has spent the last 25 years trying to create coral that's more resistant to increasing temperatures. we have found over the years that by gently bleaching corals deliberately in the laboratory we can encourage them to change their symbiotes in favour of this thermally tolerant type. just now we are starting for the first time this pilot experiment of doing this out in nature, in the field, in reefs off miami, where it is what we are calling stress hardening these corals, encouraging them to change their algae in favour of the tolerant ones that will help them to resist bleaching and hopefully persist into the future. so beautiful, isn't it?

and while they're working towards growing more resilient corals here in miami, there are of course projects going on across the globe to protect the coral we already have. nick kwek went to see one such project at the most famous coral reef in the world. the great barrier reef, australia, wonder of the world. earth's largest living thing, sprawling some 1600 miles. but this paradise could soon be lost at the hands of a very surprising vandal. crown of thorns starfish eat coral, and although they're found here naturally, recently too many have been pouring in at once due to major weather events and ocean pollution. you would think a starfish would be a cute, gorgeous thing you would see on the great barrier reef. the crown of thorns starfish, not so much. they're spiky, ugly, they can have up to 20 or 30 arms. you would think a starfish would be a cute, gorgeous thing you would see on the great barrier reef. the crown of thorns starfish, not so much. they're spiky, ugly, they can have up to 20 or 30 arms. the biggest issue with crown of thorns starfish is that they can eat up to one metre

of coral per day. when they're in plague proportions they can absolutely devastate a reef. to the rescue, the ranger bots. these underwater drones autonomously scour the reef starfish and prick them with a deadly dose of biosalt. the bots use an algorithm to identify starfish and then target them. their developers say they're 99.4% accurate. and they get smarter with time. traditionally, divers have monitored the reef by going out and doing a visual check. they record their findings on a slate — something time consuming consuming, not to mention expensive. they can only be in the water for up to three or four hours a day. they can't dive at night. whereas the ranger bot has

the capacity to be in the water for eight hours a day. it can dive at night. it also doesn't have some of the human failings that we know we have, where we see and miss things as we are getting dragged along under the water. working around the clock could make a big difference too. evidence suggests the thorny carnivores come out more at night. the ranger bots have lights, so their cameras can still see once the sun goes down. so inside these things you have got inertial sensors, pressure sensors, a gps so it knows where it's going. and it also has two computers working simultaneously. one to process the images, and one to know where it is going and understand the navigation route. the game changer is these thrusters, which allow it to go forward, backwards, up, down, leftand right, it also side to side, so when it spots the crown of thorns starfish it doesn't need to do a big loop—the—loop, it can just stop and zap them where they are. the bots are team players, too. the beauty of having this is that if we have multiple vehicles we put them here, we send them off in all directions,

they pop up 500 metres away and they already know how many they've seen. so we say, ok, zero, zero, zero, ten. that is our focus area. within 20 minutes we know roughly where we should be focusing our efforts. we will never outcompete a human and we are not trying to outcompete a human, but if we can give them the tools to extend their operational capability, that is a goal. constantly patrolling the reef, the rangers can also monitor water quality, measure coral bleaching and map the deep blue like never before. one of the issues we have about the great barrier reef is that it is so big we only know a fraction of what is going on under the water. without that information it makes it difficult for marine park managers to have a mature understanding of what's going on,

and where they need to direct their time, management, resources and people. but they are still weather dependent. too strong a current, and the poor little ranger can be thrown violently off course. for all their ingenuity, isn't the relatively small work being done by these botsjust a drop in the ocean? the great barrier reef is facing many threats. there isn't going to be a silver bullet solution. but the ranger bot is just one step in that path we can take in terms of trying to make sure that we can look after the great barrier reef on a local level while the world gets its act together on climate change. that was nick in queensland. that is all from our sustainability special from babcock ranch here in florida. we're staying in the united states for another week. next week we fly up to boston, home of mit, which always offers up 20 very, very cool innovations. looking forward to that. in the meantime, we live on twitter at @bbcclick. thank you for watching,

and we will see you soon. hello. i think saturday gave many areas of the british isles a taste of what is to come over the coming days. i will show you what i mean injust a second. but the day came to a glorious — and notjust on the river exe, but quite widely — away from the northern parts of scotland. high pressure is very much dominant at the moment, forcing the jet stream well to the north of the british isles. here, the darkening of the hues an indication of the rise in temperatures that we are expecting to see in the first half of the forthcoming week. a coolish sort of start to sunday, though, with the clear skies overnight so again, the temperatures will have dribbled away into single figures in a number of locations. but with the sun soon up in the day, i think those temperatures will soon recover and there will be a lot of fine and settled weather to be had. the frontal system still not a million miles away from the far north of scotland. the shetland islands keeping a lot of cloud for a good part of the day. a much improved situation, though, across the mainland of scotland. not too much in the way of breeze right across the piece. you will feel every bit

of those temperatures. a fraction up on where we were through saturday for a good part of england and wales, maybe northern ireland too. and certainly recovering across the heart of scotland, given that there will be a lot more sunshine and a little bit less in the way of cloud than was the case on saturday. here we are moving into the wee small hours of monday. the frontal system trying to work its way in to the far north—west of scotland. elsewhere, the night—time minima you'll notice just beginning to come up a touch —12,13,14 — quite widely across the southern half of britain, as opposed to those widespread single figures of but a few nights ago. so here we are to start the new week. and that high pressure really very much the dominant feature, although you'll notice this band of cloud — and i don't think it'll be much more than that — it is still there as a bit of a plague across the northern and western isles of scotland, maybe the far north of the mainland too. but elsewhere by this stage, we are beginning to see those temperatures really ramp up across all parts of the british isles, save perhaps for the very far north. here, on into tuesday, the high pressure is right over the top of the british isles and by this stage, the cloud will be very much more broken across northern and north—western

parts of scotland and at this stage, we could well be looking at around about 28, 29 degrees or so. many locations well on into the 20s and it is at this stage, we think, somewhere between wednesday, probably, thursday, that somebody somewhere is going to get up to around about 30 degrees or so. it may even be a touch higher than that before turning cooler later in the week. this is bbc news. i'm andrew plant. our top stories — a milestone for saudi women who've hit the roads after the controversial ban on driving is finally lifted. us homeland security says it's reunited more than 500 children who'd been separated from adults, as part of the recent zero tolerance policy on immigration. a blast rocks an election rally held by zimbabwe's president mnangagwa. he's unhurt but says it was an attempt to kill him. a dramatic last minute goal by reigning champions, germany, to keep their

world cup dreams alive. hello and welcome to bbc news.