The problem with all forms of CSP is that any clouds interfering with direct sunlight causes there to be effectively zero energy conversion, since CSP requires a point source of light like the sun on a clear day. The scattered light available when there is any type of cloud cover comes from many directions and cannot be focused. Such cloud cover can linger for days or even months. On the other hand, flat plate photovoltaic and thermal collectors create useful energy conversion even on a cloudy day. The useful energy conversion in these simple systems is proportional to the light, and do not require direct sunlight nor mechanical tracking with its substantial costs and maintenance issues. With climate change altering cloud cover in many areas, CSP is a risky investment.