Energy : the basic concepts -- How is energy used today? Present energy use -- The world's present energy system. Energy sources ; Fossil fuels ; Renewables ; Nuclear power -- The problems of the present energy system. Exhaustion of fossil fuels and energy security ; Environmental problems ; Energy costs -- Technical solutions and policies. Energy efficiency ; New technologies ; Policies -- Nontechnical solutions. Energy and lifestyle -- Appendix 1. Decimal prefixes -- Appendix 2. Common energy unit conversion factors.