{
  "slug": "solar-beam-diffuse",
  "title": "Beam and Diffuse: Two Kinds of Light, and Where a Tracker Pays",
  "url": "https://solaranalytica.com/solar-beam-diffuse",
  "summary": "Total sunlight tells you how much energy arrives, not what kind. Every kilowatt-hour is part sharp beam and part scattered diffuse light, and the ratio, not the total, decides whether a tracker or a bifacial module earns its price. The diffuse share runs from 19% on the Atacama plateau to 63% in Reykjavik: read that number before quoting a tracker.",
  "license": "Free to use with attribution to Solar Analytica (solaranalytica.com). Underlying figures are named to their public sources below.",
  "csv": "https://solaranalytica.com/reports/solar-beam-diffuse/data.csv",
  "datePublished": "2026-05-07",
  "lastReviewed": "2026-05-07",
  "sources": [
    {
      "title": "NASA POWER: surface meteorology and solar energy (GHI, DNI, DIF)",
      "url": "https://power.larc.nasa.gov/"
    },
    {
      "title": "NREL: single-axis tracking gains and system modelling (SAM / PVWatts)",
      "url": "https://www.nrel.gov/analysis/sam/"
    },
    {
      "title": "NREL: bifacial PV performance and rear-side gain",
      "url": "https://www.nrel.gov/pv/bifacial-pv.html"
    },
    {
      "title": "Sengupta et al. (NREL): Best Practices for solar resource, beam vs diffuse",
      "url": "https://www.nrel.gov/docs/fy21osti/77635.pdf"
    },
    {
      "title": "Solar Analytica methodology (irradiance profiles and data standards)",
      "url": "https://solaranalytica.com/methodology"
    }
  ],
  "figures": [
    {
      "id": "diffuse-fraction-gradient",
      "title": "The diffuse-fraction gradient. Share of annual light that arrives scattered",
      "unit": "%",
      "caption": "The deciding variable: diffuse fraction (scattered sky light as a share of total GHI) per market. Below about a quarter the sky is beam-dominated; above about half, most light is scattered. NASA POWER long-term average, from the Solar Analytica irradiance profiles.",
      "series": [
        {
          "label": "Calama (Atacama)",
          "value": 19
        },
        {
          "label": "Upington",
          "value": 20
        },
        {
          "label": "Pilbara",
          "value": 21
        },
        {
          "label": "Phoenix",
          "value": 23
        },
        {
          "label": "Ouarzazate (NOOR)",
          "value": 30
        },
        {
          "label": "Cairo (Benban)",
          "value": 32
        },
        {
          "label": "Riyadh",
          "value": 39
        },
        {
          "label": "Dubai",
          "value": 45
        },
        {
          "label": "Berlin",
          "value": 51
        },
        {
          "label": "Jakarta",
          "value": 52
        },
        {
          "label": "London",
          "value": 53
        },
        {
          "label": "Reykjavik",
          "value": 63
        }
      ]
    },
    {
      "id": "beam-vs-diffuse-split",
      "title": "Two kinds of light. Beam-on-horizontal (GHI minus DIF) vs diffuse, kWh/m2/yr",
      "unit": "kWh/m2 per year, horizontal plane",
      "valueLabel": "Beam (direct)",
      "valueBLabel": "Diffuse (scattered)",
      "caption": "Total light split into its two kinds: beam on the horizontal (GHI minus diffuse) against diffuse, per year. In the desert beam dominates four to one; in Berlin and Jakarta the scattered component equals or beats the direct. Same NASA POWER profiles as Fig 1.",
      "series": [
        {
          "label": "Calama",
          "value": 2110,
          "valueB": 511
        },
        {
          "label": "Ouarzazate",
          "value": 1521,
          "valueB": 654
        },
        {
          "label": "Phoenix",
          "value": 1647,
          "valueB": 479
        },
        {
          "label": "Berlin",
          "value": 516,
          "valueB": 549
        },
        {
          "label": "Jakarta",
          "value": 839,
          "valueB": 894
        }
      ]
    }
  ]
}