Sun Exchange, a South African firm that crowd-sources funds for solar panels and leases them to customers, plans to expand to other countries on the continent. The company, backed by a group part-owned by billionaire Patrice Motsepe’s African Rainbow Capital Investments Ltd., raised $1.4 million for a solar panel and battery-storage project at a Zimbabwean fruit and berry producer, in what it says is the biggest crowd-funded project in Africa.