Most houses use energy - lots of it. We use energy for heating, lighting, for running our household appliances - TV's, washing machines, fridges, and so on. In winter time, most houses use dozens of kilowatts of electricity every day, or the equivalent in gas.
The house in the photo, on the other hand, uses virtually nothing: most of the energy that it uses comes straight from the sun, the wind or the ground. This is an experimental house at the University of Nottingham, and it could be the kind of house that most people are living in fifty years from now.
During the daytime, it is rarely necessary to turn on an electric light, even in rooms without windows. Sunlight, or daylight, is "piped" through the house, into each room, through special high-reflection aluminium tubes. You can see how well they reflect light, by looking at the reflections of the faces in the picture!
At night, of course, energy is necessary - but most of this comes from the sun or the wind. The house is fitted with photovoltaic solar panels that generate electricity during the daytime, and a wind turbine power generator too; electricity from these can be used directly, or else stored in batteries, and used when it is needed.
For heating, the house uses direct solar energy (sunshine heating water that circulates through a radiator system), or geothermal energy. This takes low-level heat out of the ground, and uses a heat-pump to convert it into high-level heat for use in radiators - the same principle as a refrigerator, but in reverse.
As for water, most daily needs are provided for by the house's own supply; rainwater is collected on the roof, filtered, and used for all toilets, baths and showers.
If, one day, most people in developed countries live in houses like this one, most of today's pollution will have disappeared, and global warming may be a problem of the past.
fitted: equipped - generate: make, create - store: conserve, keep - geothermal: from under the ground, from the earth - in reverse: backwards - supply: provision