This is part of "Fight The Power," a series about the people, organizations and countries transforming the way we think about energy for the better.  

Hot, humid, sunny and home to a population of 5.7 million, Singapore may seem like the ideal spot for solar power generation, but that's not the case.

With a mere 278 square miles of urbanized land and filled to the brim with skyscrapers and apartments, Singapore lacks the space for solar farms found in much larger countries. Instead, Singapore still heavily relies on fossil fuels such as oil and natural gas to generate the 48.6 terawatt-hours (TWh) of electricity it consumed in 2017.

Much of that serves to keep its residents cool: Air-conditioning amounts for 36 percent of electrical use in homes.

While solar may seem like a wistful dream in the land-scarce island, Singapore's Energy Market Authority has set a target to generate 1 gigawatt peak (GWp) beyond 2020, which it says will be sufficient to power 200,000 four-room flats annually.

Here's how it will all go down.

Of rooftops and reservoirs

With a population density that ranks third in the world -- ahead of Hong Kong even -- Singapore relies on affordable and uniform-looking public housing to cater to its masses. Unlike the unique skyscrapers in the central business districts, these buildings sport flat rooftops, ideal for installation of solar panels.

In 2010, the housing board implemented a five-year S$31 million (about US$23 million, £17 million or AU$30 million converted) drive for panel installation, which has since seen over 1,898 installations islandwide. It may not seem like much, but these installations generate about 143 megawatt peak (MWp) of electricity, enough for around 28,600 homes.

These installations aren't done by the government. Instead it's solar startups, such as Sunseap, that fork out the cash to lease out space on rooftops and install their panels. Currently the startup generates about 100 MW daily that it pumps back into the energy grid. With panels expecting to last for 25 to 30 years, the company is in for the long haul, and generates revenue by selling energy credits to eco-conscious companies, such as Apple and Microsoft.

Globally, Apple is already 100 percent powered by renewable energy in the 43 countries where it has facilities. In Singapore, it draws on Sunseap's supply as well as power from its own building, which it claims is one of the largest solar installations in the island state, to power both its offices and its Apple Store.

In Microsoft's case, the company is committing to purchase about 60 MWp of power from Sunseap for the next 20 years. Announced earlier this year, the energy agreement marks Microsoft's first renewable energy deal in Asia and will be used to power its data centers locally.