Picture the scene: you wake up and brew your morning coffee using electricity from barely visible foils of solar cells covering your house facade.
You put on your shoes made from materials using recycled carbon dioxide, and as you walk out of your house past the mini wind turbine in the garden, the force of your footsteps on the pavement generates power to run the traffic lights in your street.
You get in your lightweight car - made of recycled plastic and powered by fuel made from algae - lower the window and breathe the fresh air, savouring the thought that your carbon footprint is nearly nonexistent.
That vision may become reality sooner than you think. Thousands of companies around the world are striving to find new ways to produce clean energy and to use resources as efficiently as possible.
The global push to cut carbon emissions and wean the world off fossil fuels has triggered a new industrial revolution that is being driven not just by large companies but also by innovators in garage start-ups and university laboratories.
It is a growth market that offers enormous commercial opportunities. In the next 20 years, an estimated US$5.4 trillion (Dh19.83tn) will be invested in wind farms, solar plants and other energy technologies, according to researchers at Bloomberg New Energy Finance.
Many of the ideas are as fascinating as they are promising. But making them commercially viable is a major challenge that takes patience and money, both of which have been in short supply during the financial crises of recent years.
Nevertheless, the market is crisis-proof in the long run because resource efficiency holds the key to tackling the megatrends confronting the world in the coming decades: population growth, the expansion of cities, the scarcity of natural resources and climate change.
Torsten Henzelmann, a green-tech expert and a partner at Roland Berger Strategy Consultants in Germany, says the global market for environmental technology and resource efficiency currently totals more than €2tn (Dh10.02tn) and will grow at an annual rate of 5.6 per cent on average from last year to the end of 2025.
"In terms of market volume, innovations in the areas of intelligence and automation are in especially strong demand, solutions that control processes to boost energy efficiency," Mr Henzelmann says. "For example, there are firms working on systems that can measure the pulse of plants to determine when they need water."
One such firm is Zim Plant Technology, from Hennigsdorf about 20 kilometres north-west of Berlin, which has developed a system that measures and monitors plants' thirst in real time. It says this could enable farms to cut water consumption by up to 30 per cent. Sensors the size of a thumbnail are attached to leaves to measure the pressure in plant cells. When the cells lose water, the pressure drops.
"That way we always know how thirsty the plants are and only irrigate when necessary," says the start-up's founder, Ulrich Zimmermann.
In the hunt for clean energy, a number of firms have hit on the idea of converting algae into biofuel. It's an attractive concept because algae have the added advantage of consuming CO2 as they grow and they can be cultivated on industrial wasteland rather than using up valuable arable land.
The German company Phytolutions has been running a small research plant that grows marine microalgae near Cologne since 2008 and is now looking for investors to expand the project.
It needs economies of scale to become profitable, however. Stefan Rill, who co-founded the project, believes that a price of €1.70 per litre of algae oil would be competitive and could be reached this decade - if he got the opportunity to launch mass production.
Germany is a strong player with a 15 per cent share of the world's green-tech market, a position it will be able to maintain in the coming decade despite an expected onslaught of new competitors, says Mr Henzelmann.
"Companies in this country get enough money when it comes to converting an idea into a prototype, but things get more difficult when it comes to producing a marketable product on an industrial scale. In this area there's a lack of financing opportunities."
The British start-up Pavegen says it is well on the way to taking that step. It has come up with the idea of harvesting energy through rubber paving slabs that generate and store kinetic power when stepped on. The inventor, Laurence Kemball-Cook, says the slabs can produce large amounts of electricity in "heavy footfall environments" such as busy city streets, where wind or solar power are less efficient means of producing power.
"It provides a way that people can save energy without realising it," he says. "All they have to do is walk down the road."
The system can power lights or other applications. The slabs were installed at London's West Ham underground station during the Olympics last summer and in other demonstration events.
"Now we're starting to do larger scale projects," says Mr Kemball-Cook.
For many, carbon dioxide is nothing but a dirty, damaging product of the industrial age - the source of global warming, melting glaciers and rising sea levels. The feared gas, they believe, should be avoided at all costs or, if unavoidable, stored underground and forgotten about.
But researchers are coming up with new ways to harness the pollutant by using it as a raw material. One day, it could be a component in most everyday goods - from sandals to medical drugs.
Skyonic, a start-up based in Texas, plans to commercialise technology that turns carbon emissions into chemicals such as baking soda. Other firms are using CO2 in the production of cement and plastic.
SunFire, a start-up based in Dresden, Germany, even plans to turn carbon dioxide into synthetic fuel, using green electricity in the process. The company says its system already works and that it will start up a plant by 2016 to produce five tonnes of petrol, diesel or kerosene per day.
The race is on to find new types of biofuel that do not require vast swaths of farmland needed for food production. Firms are working on processes to turn old tyres into oil, waste wood into gas, engine heat into electricity and biological waste into coal.
Heliatek, another firm based in Dresden, is developing low-cost, lightweight, organic solar cells on flexible plastic foils that can be applied to window blinds, car roofs and entire building facades.
The cells use molecules to absorb light and convert it to electricity. Heliatek says its cells absorb a broad spectrum of light and also deliver excellent performance in low-light conditions.
Similar cells are being developed by about 20 other companies around the world, but Heliatek, which works with two universities, says it is the market leader with a world record 12 per cent cell efficiency.
Here's a novel way to boost efficiency: a Berlin start-up, Chido's, gathers used coffee grounds and grows gourmet mushrooms from it. Its manager, Philipp Buddemeier, says it is a much more resource-sparing way to produce mushrooms than conventional farming.
"Per kilo of [standard-grown] mushrooms, three to four kilos of fresh wood or straw are needed," he says. Chido's mushrooms do not need that.
The idea has won the firm an award for sustainability, not just because it is an intelligent way to use rubbish but also because it serves as a model for a workable recycling economy and for the global trend of urban farming.
Energy storage is a particular challenge with renewable power generation because of the fluctuations in power supply resulting from the wind and the sun.
One US firm, LightSail, has come up with an idea to store energy using air and water. When wind turbines produce more electricity than needed, an engine uses that power to compress air in a container. When that power is needed, the pressurised air is released, driving a generator. The heat produced in the process is then converted back to conventional power.
Danielle Fong, the chief scientist at the company, is convinced the system could one day be used to provide entire cities with power for hours.
Many innovations will fail, not necessarily because they are a bad idea but because they are not commercially feasible.
"There are many exceptional innovations which seem interesting at first sight. But then the question arises, who is going to buy these solutions, who is going to finance them?'" says Mr Henzelmann. "Not every technical innovation makes economic sense.
"Take a wind turbine that takes in wind from below via vertical-axle rotors to produce power, or the swimming buoy that generates electricity via the lift caused by waves. Or a small power plant that floats by the bank of a river and produces power from the current without blocking the river."
These ideas may be commercial non-starters, but the market will keep on expanding because it is vital to the welfare of an ever-growing world population.
Roland Berger predicts the industry will be worth some €4.4tn by 2025.
And that, it insists, is not just a load of hot air.