How many orders were made by Alan Barnes in 2015 at the Central superstore?
in 2015 refers to "Order Date" = '2015%'
SELECT COUNT(DISTINCT T2.`Order ID`) FROM people AS T1 INNER JOIN central_superstore AS T2 ON T1.`Customer ID` = T2.`Customer ID` WHERE T1.`Customer Name` = 'Alan Barnes' AND STRFTIME('%Y', T2.`Order Date`) = '2015'