If you had no income, the non-refundable portion of any education credit you might be eligible for would have nothing to be applied to. In other words, you can't get a credit since you have no taxable income or tax liability for that credit to decrease.

Only the American Opportunity Tax Credit can be received as a refund, but that credit can only be used 4 times per student and also is not available to grad students. 

Below are the filing requirements for 2018:

FILING REQUIREMENTS FOR TAXPAYERS: UPDATED FOR TAX YEAR 2018 

Single

under 65 $12,000

65 or older $13,600

Head of Household

under 65 $18,000

65 or older $19,600

Married, Filing Jointly***

under 65 (both spouses) $24,000

65 or older (one spouse) $25,300

65 or older (both spouses) $26,600

Married, Filing Separately

any age $5

Qualifying Widow(er) with dependent child

under 65 $24,000

65 or older $25,300

FILING REQUIREMENTS FOR DEPENDENTS:

Single dependents—

Were you either age 65 or older or blind?

No. You must file a return if any of the following apply. 1. Your unearned income was more than $1,050. 2. Your earned income was more than $12,000. 3. Your gross income was more than the larger of— a. $1,050, or b. Your earned income (up to $11,650) plus $350.

Yes. You must file a return if any of the following apply. 1. Your unearned income was more than $2,650 ($4,250 if 65 or older and blind). 2. Your earned income was more than $13,600 ($15,200 if 65 or older and blind). 3. Your gross income was more than the larger of— a. $2,650 ($4,250 if 65 or older and blind), or b. Your earned income (up to $11,650) plus $1,950 ($3,5500 if 65 or older and blind).

Married dependents—

Were you either age 65 or older or blind?

No. You must file a return if any of the following apply. 1. Your gross income was at least $5 and your spouse files a separate return and itemizes deductions. 2. Your unearned income was more than $1,050. 3. Your earned income was more than $12,000. 4. Your gross income was more than the larger of— a. $1,050, or b. Your earned income (up to $11,650) plus $350.

Yes. You must file a return if any of the following apply. 1. Your gross income was at least $5 and your spouse files a separate return and itemizes deductions. 2. Your unearned income was more than $2,350 ($3,650 if 65 or older and blind). 3. Your earned income was more than $13,300 ($14,600 if 65 or older and blind). 4. Your gross income was more than the larger of— a. $2,350 ($3,650 if 65 or older and blind), or b. Your earned income (up to $11650) plus $1,650 ($2,950 if 65 or older and blind)

CLICK HERE for IRS Pub 501 Exemptions, Standard Deduction, Filing Information