Efficiently generate very large Excel file in .NET?

I need to create a very large Excel file from an ASP.NET MVC site, but I am using memory limits using the Open XML SDK. Is there a memory efficient way to create such a file?

For reference, I am trying to create a spreadsheet with approximately 500,000 rows of 20 columns each. The dataset itself fits perfectly into memory, but the Open XML SDK quickly eats up all available memory.