Quartz sand/graphite composite molten salt heat transfer and heat storage medium and preparation method thereof

A heat transfer and storage medium comprising silica sand compounded with a heat transfer and storage molten salt system,

• wherein a weight proportion of said silica sand in said heat transfer and storage medium is 10% to 50%,
• said heat transfer and storage molten salt system selected from a group consisting of a binary nitrate molten salt system and a ternary nitrate molten salt system, wherein:
• the binary nitrate molten salt system is a KNO3—NaNO2 system comprising, in relative parts by weight, 30-40 parts potassium nitrate, and 60-70 parts sodium nitrite;
• and
• the ternary nitrate molten salt system is a KNO3—NaNO3—NaNO2 system selected from a group consisting of following formulas, in relative part by weight:
• 40 parts potassium nitrate, 15 parts sodium nitrate and 30 parts sodium nitrite;
• 80 parts potassium nitrate, 5 parts sodium nitrate and 10 parts sodium nitrite;
• and
• 60 parts potassium nitrate, 15 parts sodium nitrate and 50 parts sodium nitrite.