Solar energy（太阳能） is one of the cleanest and most plentiful（丰富） sources（来源） of energy.
Solar power depends on sunlight, so in cloudy weather（阴天） and at night, no power is generated（产生、生成）.
Wind energy is non-polluting（无污染） but it’s only useful in places where there is a lot of wind.
Wind turbines（风力涡轮机） convert（转换） the kinetic energy（动力能） of wind into mechanical（机械的） power.
Nuclear energy（核能） is efficient（有效率的） and doesn’t produce（生产） carbon（碳） gases as a waste product.
The dangers of nuclear power（核动力、核电） include deadly（致命的） radioactive（放射性的） waste products.
A major（主要的） source of energy comes from the burning（燃烧的） of fossil（化石） fuels（燃料） such as coal（煤） and oil（石油）.
When we burn fossil fuels, waste gases such as CO2 are produced.
Fossil fuels remain（依然、保持、剩下） the largest source of energy for most countries.
Hydropower（水力发电） comes from the kinetic energy of falling（落下） water.
Output（产量） is reliable（可靠的） and can be regulated（调节、控制、管理） to meet the demand（需求、需要） except during the period of drought（干旱）.
We need to reduce（减少） the use of fossil fuels to produce energy.
One of the main problems we face is how to reduce the use of fossil fuels to produce energy.
Dams are expensive to build and affect wildlife such as fish.
