Google is just $10 million dollars short of having invested $1 billion into clean power projects. On Thursday Google announced that it’s put another $75 million into a wind farm in Iowa, bringing its total funds invested in clean energy projects to $990 million.

The Iowa wind farm — called the Rippey Wind Farm and located in Greene County — is owned by RPM Access and its 20 turbines are already online, with a capacity to produce 50 MW of wind power (enough to power 15,000 homes). The power will be bought by Central Iowa Power Cooperative (CIPCO).

Google has a data center in Council Bluffs, Iowa, and has already invested in other clean power projects in the region as well, including a 114 MW wind farm in Iowa owned by NextEra Energy Resources. Google is investing in clean power projects because it wants to use more clean power for its data centers — the search engine giant plans to have about a third of the power for its data centers come directly from clean power.

Once Google invests in a clean power project, its a tricky move to actually get that power used directly for its data center. Google has often said that it’s making these investments partly to get a return over time on the investment. But a couple months ago, for the first time, Google said it will buy clean energy from a utility in Oklahoma to directly power one of its data centers in Oklahoma.

Here’s some of Google’s clean power investments:

Here are most of Google’s clean power investments to date:

• SolarCity rooftop solar fund. Google has created a $280 million fund with home solar installer SolarCity. This is Google’s largest investment in clean power to date, and its first in home rooftop solar.
• Solar panel projects in Sacramento Calif: Google put $94 million into four solar panel projects, which are being built by Recurrent Energy close to Sacramento, Calif. This was Google’s first investment in utility-scale grid-connected solar panel projects.
• Buying wind power from a utility directly to power a data center in Oklahoma: For the first time in September 2012, Google said it would buy clean energy from a utility to directly power one of its data centers in Oklahoma.
• Clean Power Finance. Google invested $75 million into a solar fund for startup Clean Power Finance. Clean Power Finance will use the money to support solar rooftop projects by third party installers.
• The world’s largest wind farm — in Oregon. Google is investing $100 million in the world’s largest wind farm, the 845 MW Shepherds Flat project under construction in Oregon.
• North Dakota wind farm. Google is investing $38.8 million into 169.5 MW worth of wind projects developed by NextEra Energy Resources in North Dakota.
• East Coast wind farm backbone. Google has invested part of the fund for an East Coast transmission line that is meant to link offshore wind farms, and which recently got an approved rate of return for the project at 12.59 percent.
• Wind power from Iowa wind farm. Google’s first deal for its subsidiary Google Energy — which can buy and sell power on the wholesale electricity markets — plans to buy wind power from 114 MW of wind energy via a wind farm in Iowa owned by NextEra Energy Resources.
• Wind power from Oklahoma wind farm. Google’s second deal via its subsidiary Google Energy is to buy 100 MW of power from a wind farm that’s under construction in Oklahoma by NextEra Energy Resources.
• BrightSource’s solar thermal project. Google plans to invest $168 million into a solar thermal project being built by startup BrightSource Energy in California’s Mojave Desert.
• German solar project. Google is investing €3.5 million ($5 million USD) into a solar photovoltaic farm in Brandenburg an der Havel, Germany, which is near Berlin.
• Greentech startups (these are small investments). Google (through a combo of Google Ventures and Google.org) has invested in at least nine “greentech” startups, including battery maker ActaCell, electric vehicle maker Aptera, efficient car maker Next Autoworks, geothermal company Alta Rock, neighbor-to-neighbor car sharing company RelayRides, weather insurance company WeatherBill, smart grid company Silver Spring Networks, biofuel maker Cool Planet Biofuels, and efficient power gear conversion tech startup Transphorm.